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 DOI: 10.1177/0042098009360229

2010 47: 3035 originally published online 28 June 2010Urban StudMiquel-Àngel Garcia-López and Ivan Muñiz

BarcelonaEmployment Decentralisation: Polycentricity or Scatteration? The Case of

  

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47(14) 3035–3056, December 2010

0042-0980 Print/1360-063X Online © 2010 Urban Studies Journal Limited

DOI: 10.1177/0042098009360229

Miquel-Àngel Garcia-López and Ivan Muñiz are in the Department of Applied Economics, Universitat Autònoma de Barcelona, Edifici B, Facultat de Ciències Econòmiques, Campus Bellaterra, Bellaterra, Barcelona, 08193, Spain. E-mail: miquelangel.garcia@uab.cat and ivan.muniz@uab.es. Both authors are members of GEAP-XREAP (Grup d’Anàlisi Econòmica Aplicada – Xarxa de Referència en Economia Aplicada).

Employment Decentralisation: Polycentricity or Scatteration? The Case of BarcelonaMiquel-Àngel Garcia-López and Ivan Muñiz

[Paper first received, May 2008; in final form, September 2009]

Abstract

At the present time, most large cities in the world are polycentric and, at the same time, they are undergoing processes of employment decentralisation and deconcentration. It has been argued that polycentricity is just an intermediate stage between monocentricity and a more unstructured, chaotic and amorphous location model, scatteration. For the case of the polycentric Barcelona, the aims of this study are to test: whether its employment is moving from polycentricity to scatteration; and, whether its employment location model is increasingly random and unstructured. The results show that, in spite of the decentralisation and deconcentration processes, employment concentrated in centres still represents a significant percentage of total employment and new sub-centres have emerged in the periphery. What is more, the results also show an increasing influence of employment sub-centres on employment location and density conditions. As a result, polycentricity has been reinforced.

environmental effects, the scatteration of employment increases population scattera-tion, with the consequent increase in land consumption. It also increases the difficulty in offering competitive public transport, meaning that a car-based mobility model tends to prevail, which leads to higher CO2 emissions (Newman and Kenworthy, 1989; Kahn, 2000; Camagni et al., 2002; Muñiz

1. Introduction

How will employment be distributed in spatial terms in the city of the future? This is an important issue, given the social, envi-ronmental and economic impacts involved (Lang and Lefurgy, 2003). From a social point of view, the distancing of employ-ment from the population is especially prejudicial to social groups with the most limited mobility (Kain, 1992). In terms of

3036 MIQUEL-ÀNGEL GARCIA-LÓPEZ AND IVAN MUÑIZ

and Galindo, 2005). According to standard economic theory, excessive scatteration of employment is due partly to the failure to properly internalise the positive externalities which are generated when firms are located in a dense and compact space, meaning that the concentration of employment may be below what would be efficient in social terms (Richardson, 1995; Anas et al., 1998).

The main argument used by those pre-dicting an increased scatteration of employ-ment is that improvements in private transport and telecommunications have made agglomeration economies less impor-tant (Carlino, 1985; Richardson, 1995; Gordon and Richardson, 1996; Pfister et al., 2000; Lang, 2003). On the other hand, those who state that decentralised employment tends to concentrate in smaller secondary centres maintain that physical proximity is still essential (Cervero, 1989; Hartshorne and Muller, 1989; Garreau, 1991; Stanback, 1991). The formation of sub-centres would permit departure from the congestion of traditional centres without thereby losing the agglomeration economies that can arise in conditions of high density, albeit not as high as those in the CBD. Theoretical discussion on the spatial structure of the cities of the present and future is therefore mainly based on the validity or otherwise of the agglomeration economies which in the past led to their formation and growth (Richardson, 1995; Henderson and Mitra, 1996; White, 1999; Glaeser and Kahn, 2004).

In a popular and controversial article, Gordon and Richardson (1996) wondered which of the two employment decentralisa-tion models—the polycentric or scattered model—tends to prevail, which led to a long list of studies applied to various cities which examined recent trends in order to answer the question (Pfister et al., 2000; Coffey and Shearmur, 2002; Shearmur and Coffey, 2002; Shearmur and Alvergne, 2003; Lee, 2007). Two controversial predictions arose from

Gordon and Richardson’s (1996) study. First, polycentricity might be an intermediate spatial stage between monocentricity and scatteration. Secondly, if distance is less and less important, the pattern of employment location will tend to be increasingly random, unstructured and amorphous. Studies such as those of Anderson and Bogart (2001), Leslie and Ó hUallacháin (2006), Shearmur et al. (2007) and Giuliano et al. (2007) found empirical evidence opposite to such predic-tions. They proposed a more subtle use of the concept of agglomeration economy. It is possible that improvements in transport and communications have expanded the radius of action of agglomeration economies, but this does not mean that they are equally accessible throughout the metropolis as a whole. Furthermore, the location of certain activities has probably been affected by the expansion of its radius of action, while oth-ers continue to need frequent face-to-face contacts (Anas et al., 1998; Phelps, 2004; Giuliano et al., 2007).

The aim of this study is to test whether, in the case of the Barcelona metropolitan region between 1986 and 2001, a polycentric urban region in which the employment has decentralised and deconcentrated intensely during the past 20 years, the aforementioned predictions are verified. Is employment mov-ing from polycentricity to scatteration? Is the employment location model increasingly random and unstructured?

The paper continues with section 2, where both concepts, polycentricity and scatteration, are outlined through a literature review. In section 3, a brief presentation of the BMR is made. The proposed methodology to study these questions regarding the polycentric-ity–scatteration discussion is presented in section 4. The main results concerning the spatial organisation of employment in the BMR and its changes are discussed in section 5. Finally, the principal conclusions of the study are presented.

EMPLOYMENT DECENTRALISATION IN BARCELONA 3037

2. Polycentricity and Scatteration: Two Alternative or Complementary Models?

2.1 Scatteration versus Concentration

Scatteration. The idea that, in the future, thanks to technological progress it will be possible to live in large spaces, in direct contact with nature, finally escaping the con-gestion of urban centres, but without losing any of the advantages of city life, is at least as old as Frank Lloyd Wright’s ‘broadacre city’ or the ideas of the Russian disurbanis-ers of the early 20th century. In the US, and in Europe some time later, there was an intense process of population decentralisa-tion from the centres towards the outskirts, thanks to increases in income, but above all due to the popularisation of the automo-bile. Employment subsequently followed the population (Hartshorne and Muller, 1989; Cheshire and Hay, 1989; Stanback, 1991; Mieszkowski and Mills, 1993; Hall, 1997). The effect of the fall in transport costs on the decentralisation of employment (Carlino, 1985; Richardson, 1995; Gillham, 2002) was reinforced by the revolution in telecommunications, which seemed to hail a future characterised by working at home (telecommuting), video conferences and a dense network of information between firms and between premises in the same firm which would diminish the importance of physical proximity. The basic idea was that virtual communication can replace face-to-face contacts (Pressman, 1985; Castells, 1989; Fishman, 1998; Cairncross, 1997; Kloosterman and Musterd, 2001). Various authors have coined clever names to describe this new city, in which population and employment have dispersed to the point where the classic image of the compact city has almost completely faded away, including the ‘information city’ of Castells (1989) as a metaphor for a fragmented space based around information and production networks; the

‘telepolis’ or ‘remote city’ of Echevarría (1996), in which the urban archipelago assumes a spa-tial scale of previously unknown dimensions; the ‘flex-space’ of Lehrer (1994) or the ‘città diffusa’ of Indovina (1998), as a representa-tion of a profound change in the relationship between the urban and the rural, character-ised by the dissolution of previously well defined limits; and the ‘edgeless city’ of Lang (2003), the expression of a new discontinu-ous and scattered pattern of office location. In the final analysis, all these categories, albeit with different nuances, assume a vision, a projection of the future, in which the city as we have so far understood it would disappear (Fishman, 1998).

Concentration.  During the 1980s, various authors in the fields of economics, sociology and geography turned their attention towards a number of industrial environments typified by the dynamism of small firms, the localised nature of the externalities that they generated and their technological dynamism. They were all presented as the geographical expres-sion of a production model that was mov-ing away from Fordism (high fixed capital costs, internal economies of scale, long and standardised series of production, internal division of labour, stable and predictable demand) towards flexible specialisation (R&D-intensive processes, external econo-mies of scale, short production series, exter-nal division of labour, unstable and changing demand) (Piore and Sabel, 1984). Industrial districts and technopoles (Becattini, 1990; Scott, 1988; Storper and Scott, 1986; Storper and Venables, 2004) were possibly the most stylised versions of the new geography of post-Fordist production spaces, in which the concentration of employment seemed to be an essential condition. Proximity not only cut transport costs, but thanks to local links, also facilitated obtaining agreements based on trust built on long-standing stable relationships (Best, 1990; Harrison, 1992).

3038 MIQUEL-ÀNGEL GARCIA-LÓPEZ AND IVAN MUÑIZ

This approach seriously called into question the prediction of a future defined by the scat-teration of employment, as concentration and proximity appeared to be the most favourable scenario for the production model that seemed to be prevailing (Clark and Kuijpers-Linde, 1994; Audirac, 2002; Lee, 2007)

Despite advocating the advantages of spatial concentration, this line of study has focused on the industrial sector and, in the majority of cases, was not accompanied by any discourse on spatial structure. This came some time later, when authors such as Garreau (1991) focused their attention on the formation of employment centres on the outskirts of urban areas. ‘Edge cities’ are the expression of the benefits of proximity for activities such as finance, insurance and specialised firm ser-vices. It is therefore an approach focusing on the services sector that includes a metropoli-tan discourse. The creation of edge cities able to compete with traditional CBDs pointed to the transformation of metropolitan regions from monocentricity to polycentricity. Urban economics had to reformulate its theoreti-cal models to include sub-centres (Sullivan, 1986; Wieand, 1987; Sasaki, 1990; Fujita et al., 1997; White, 1999) and intense work was done focusing on a search for methods enabling them to be identified in a simple, replicable manner that was as objective as pos-sible (Gordon et al., 1986; McDonald, 1987; McDonald and McMillen, 1990; Giuliano and Small, 1991; Song, 1994; Cervero and Wu, 1997; Forstall and Greene, 1997; McMillen and McDonald, 1997, 1998; Bogart and Ferry, 1999; Anderson and Bogart, 2001; Craig and Ng, 2001; Shearmur and Coffey, 2002).

The geography of employment in the con-temporary city. We have drawn a dividing line between authors who anticipate a trend towards the scatteration of employment and those who appear to favour concentra-tion. This separation, which is useful for reasons of clarity, is nonetheless somewhat

artificial when the aim is to describe the basic features of modern cities. There are many cases in which an author that is clearly identified with the school of thought that predicts growing dispersion states that there are still powerful centripetal forces which explain the existence of spaces dominated by concentration (Pressman, 1985; Hall, 1985; Lang and Lefurgy, 2003). The opposite is also true—authors who believe in polycentricity have examined the role of congestion and high land prices in the increasing dispersion of numerous industrial plants towards the suburban outskirts (Storper and Harrison, 1991). In short, the portrait of the contem-porary metropolis that is usually painted, by both schools, is quite similar: it is a landscape in which sub-centres of employment co-exist with large areas in which employment is dispersed

The polycentric pattern, interesting and important though it may be, co-exists with a great deal of local employment dispersion (Anas et al., 1989, p. 1443).

The difference lies in which of these two geog-raphies (concentrated or dispersed spaces) they have chosen to study in depth and how they believe they will evolve in the future.

2.2 From the ‘Polycentricity vs Scatteration’ Debate to New Approaches to Employment Spatial Structure

The future of  the urban form: polycentricity or scatteration? The relative calm in which both schools of thought had co-existed for some time ended with the controversial work by Gordon and Richardson (1996) which considered which of these two models, the polycentric or the scatteration, will tend to prevail in the light of recent changes in the location of employment. By examining the case of Los Angeles, they concluded that, in the same way as monocentricity had evolved towards polycentricity, polycentricity was evolving towards scatteration. The question,

EMPLOYMENT DECENTRALISATION IN BARCELONA 3039

considered in this light, has very questionable implications. First, by basing its explanation on the strength of the centrifugal forces which acted on a global scale (the fall in transport costs and improvements in telecommunica-tions), it implied acceptance of a sequential model that was valid for all cities, although possibly with different schedules. Secondly, a zero-sum logic was imposed, according to which only one of the two models could pre-vail. Thirdly, focusing the discussion on the behaviour of employment, without nuances, without discriminating between different types of activities, excluded the possibility that there were different future scenarios for different sectors. Fourthly, theoretical discussion focused on the radius of action of agglomeration economies. If their impact was limited, then polycentricity would prevail but, if the advantages spread to the edges of the metropolis, then scatteration would prevail. As a result, it did not take into consideration the fact that there are different types of agglomeration economies, that these can have different radii of action and that these in turn can vary in different ways due to technologi-cal changes (Phelps, 1992; Phelps and Ozawa, 2003).1 Finally, it was implicitly assumed that the geography of sprawl was characterised by its lack of form and structure, and that it was a discontinuous and not very dense space in which employment was located randomly.

Empirical evidence and alternative appro-aches to the future of the urban form.  The study by Gordon and Richardson (1996) has been the benchmark for numerous stud-ies applied to various metropolitan regions. Gordon and Richardson (1996) identified the employment sub-centres in Los Angeles using a criterion based on the density of journeys and then examined the variation between 1970 and 1990 in the percentage of employment concen-trated in the CBD and in the sub-centres and compared it with the variation in the rest of the metropolis, with the result being that

the percentage of employment outside these centres increased more significantly than inside them. Pfister et al. (2000) found similar results for the case of Sydney. The same trend was noted in the study by Lang (2003) which shows that consumption of land for offices increased more intensely in areas that could not be con-sidered either as the CBD or edge cities. He cleverly called these settlements ‘edgeless cities’.

Some studies have questioned Gordon and Richardson’s (1996) predictions regard-ing the relationship between polycentricity and scatteration, as well as the trend to an unstructured and amorphous model. As regards to the supposed temporal state of the polycentric model and the unstoppable emergence of the scatteration, Lee (2007) found significant differences in the evolu-tion of a group of American cities. Portland and Philadelphia tended clearly towards scatteration, but the CBDs of New York and Boston remained strong and sub-centres were increasingly important in Los Angeles and San Francisco. Shearmur and Alvergne (2003) showed that employment in Paris was not evolving towards a dispersed model but instead a polycentric one, and noted that a territorial policy aimed at maintaining the strength of the region’s centre and concentrat-ing peripheral population and employment in villes nouvelles was a key factor. In a study applied to four Canadian cities, Shearmur and Coffey (2002) found no evidence for the prediction that scatteration would prevail over polycentricity. The main conclusion that can be drawn from the studies by Lee (2007), Shearmur and Alvergne (2003) and Shearmur and Coffey (2002) is that history, geography and planning interact with improvements in transport and telecommunications, meaning that the existence of a universal law, according to which polycentricity would be no more than a temporary state between monocentricity and scatteration, would be questionable. Another study critical of the predictions of Gordon and Richardson is that of Giuliano et al. (2007) in

3040 MIQUEL-ÀNGEL GARCIA-LÓPEZ AND IVAN MUÑIZ

which, although empirical evidence is found for the scatteration of employment in Los Angeles, it is accompanied by the appearance of new sub-centres. The account by Gordon and Richardson (1996) suggested that sub-centres would dissolve, leading to a gener-alised scatteration, but the emergence of new sub-centres seems to suggest that scatteration and polycentricity are two processes that can arise simultaneously without one displacing the other.

As for the prediction of an increasingly unstructured spatial organisation of employ-ment, various studies have shown that employment labelled as ‘dispersed’ some-times presents a clearly identifiable structure (Anas et al., 1998; Anderson and Bogart, 2001; Desmet and Fafchamps, 2005; Leslie and Ó hUallacháin, 2006; Shearmur et al., 2007). Like the findings of Pressman (1985), they find intense growth in employment outside but near the sub-centres. In other words, even if we accept the hypothesis that some sub-centres are decentralising, it seems clear that they continue to determine the location of employment.

In the European case, several studies have analysed not only phenomena related to the scatteration of employment, but also the emergence of polycentric configura-tions in which sub-centres adapt to the new functions of the post-Fordist production system (Harding, 1997; van den Berg et al., 2001; Phelps and Parsons, 2003; Phelps, 2004; Phelps et al., 2006). The diversity of examples and their idiosyncrasies show the need to take into consideration path-dependency arguments. Regarding the main goals of this research, the main problem with these works is the use of very different empirical methodologies and, moreover, without approaching directly the questions raised in this study.

In the following sections, we analyse both Gordon and Richardson’s (1996) predictions in the case of the Barcelona metropolitan

region (BMR). The BMR is one of the most important European metropolises and it is an excellent case study for our purpose because, first, during the past 20 years, it has been undergoing decentralisation and decon-centration processes affecting employment and, secondly, from a static point of view, its employment spatial structure has been related to a polycentric location model based on a big main centre and several sub-centres (Muñiz et al., 2008). The question that arises is whether these processes are changing the location model of employment. Are employ-ment centres, in general, and sub-centres, in particular, losing employment in absolute and relative terms? That is, are scattered locations replacing polycentric locations? On the other hand, how is the influence of sub-centres on employment location evolving? Is it decreas-ing and, thus, is a more unstructured, amor-phous and chaotic location model emerging? To sum up, the polycentricity–scatteration discussion is studied.

3. The Barcelona Metropolitan Region: A Preview

3.1 Main characteristics

The Barcelona metropolitan region is the area consisting of 164 municipalities (Figure 1) which the Catalan territorial organisation laws (1987) established as the benchmark administrative unit for planning (Barcelona Metropolitan Territorial Plan). The legisla-tors’ aim was for the area covered by the plan to be the same as what they called the ‘real city’—i.e. a large area with various identi-ties, but one which was economically and functionally integrated. The municipalities within the BMR are similar to those that arise from applying the standard North American methodology for the delimitation of met-ropolitan areas (Office of Management and Budget, 1990; Burns et al., 2001) based on the intensity of commuting between municipali-ties or census tracts.

EMPLOYMENT DECENTRALISATION IN BARCELONA 3041

With over 65 per cent of the Catalan popula-tion (4 390 000 inhabitants) and employment (1 822 000 jobs),2 the BMR is the main urban agglomeration in Catalonia and is in second place in Spain at a very short distance behind Madrid. In European terms, it is the fourth most populated urban region, the eighth largest and the third most densely popu-lated (Mancomunitat de Municipis de l’Àrea Metropolitana de Barcelona, 1995). The city of Barcelona is the main centre of the region and the continuous built-up area surpasses its administrative limits, taking in 12 adjacent municipalities. Five outlying municipalities (Mataró, Terrassa, Sabadell, Vilafranca and Vilanova) are medium-sized towns which in the past accounted for a significant propor-tion of the services consumed by nearby towns. Today, they still have a high level of self-containment and a net balance of entries in journeys due to work or study.

The very intensive growth in population and employment that took place in Barcelona in the 1950s and 1960s led to the appearance of an extremely dense built-up first ring with housing estates. Since the 1980s, population decentralisation towards smaller towns fur-ther away has led to a transformation of many second homes into first homes. Albeit with some delay, employment is also undergoing an intense decentralisation process. Many firms have moved towards the outskirts in search of proximity to access to main roads, the medium-sized towns have absorbed part of the decentralised employment and the smaller towns have seen their volume of employment increase with the creation of small industrial estates and the provision of nearby services for the population (schools, shops, nurseries, surgeries, etc.).

One of the unusual geographical features of the BMR is the high percentage of forest

Figure 1. Developed land and municipal divisions in the Barcelona Metropolitan Region. Source: authors’ elaboration using Superfície Urbanitzada and Divisió Administrativa Municipal (maps produced by the Departament de Medi Ambient (DMA) and Institut Cartogràfic de Calunya (ICC) respectively and available at the DMA website (http://mediambient.gencat.cat/cat/el_departament/cartografia/docs/cartografia_referencia.jsp).

3042 MIQUEL-ÀNGEL GARCIA-LÓPEZ AND IVAN MUÑIZ

land (68 per cent).3 Orography (Figure 2) has determined the model of urban expansion to a very great extent: transport infrastructures (train, and highways and freeways) (Figure 3) and the main settlements are located in the often narrow passes between hills, in valleys (Miralles, 1997; Muñiz et al., 2003, 2008). The maps of the gross municipal employ-ment density (jobs/hectare) in 1986 and 2001 (Figures 4 and 5) show the concentration of employment in the central area and on the northern coastal axis, but also the pres-ence of municipalities with a high density of employment in the inland region, following the transport axes. The main change that can be detected when the two years are compared is the increase in employment density in the municipalities close to Barcelona on the northern axis, which make up a compact area of high density.

3.2 Employment Decentralisation and Polycentricity in the BMR: Previous Studies

Employment  decentralisation  in  the BMR. Only a few studies have explored the causes of employment decentralisation in the BMR. Carreras (2002) maintains that the transfer of industries is due to the need to expand the land surface they occupy and the lack of free building sites in Barcelona, and also stresses the role of the incompat-ibilities between residential and industrial uses in the central area. The arguments related to the changes undergone at a global scale—which from the 1970s onwards led to the shift from a Fordist production model to a flexible one based on short production series, the decentralisation of services and a greater preponderance of small and medium-sized firms in medium-sized municipalities—have also been echoed in studies such as those by Trullén et al. (1989) and Miralles (1997). Other possible causes, such as the increase in land prices in the centre of the city, the growing provision of services to a previously

decentralised population, the greater func-tional integration of the metropolis and the revolution in communication technologies, have sadly not been examined in detail.

Two questions need to be asked with regard to territorial planning. Has employment decentralisation been driven by a general planning at the metropolitan scale? And, what has been the capacity of planning to channel the market dynamics correctly? The answer to the first question is that there has been no metropolitan territorial planning as such. It has been the municipalities themselves, in an unco-ordinated and fragmented way, and by means of successive modifications of the existing and superimposed general plans, who have led the process, with all the inconsistencies, overlaps and vacuums that this entails (Vecslir, 2005). As far as the rela-tionship between planning and the market is concerned, it seems that the development of the metropolitan network of infrastructure has had more influence than urban planning decisions

The ‘spontaneity’ of the process ... would thus lie in its self-organising planning and development, which, in the absence of a supra-municipal plan that jointly co-ordinates the development of territorial infrastructures and growth environments, imposes on local planning its own logic based on accessibility and the economics of localisation, while ignoring municipal limits (Vecslir, 2007, p. 52).

Polycentricity  in  the  BMR. Few previous studies have attempted to identify the BMR’s sub-centres. However, there have been stud-ies that, without it being their main objec-tive, use an extremely simple criterion, such as the population threshold (Martori and Suriñac, 2002) or employment threshold (Asensio, 2000). There are somewhat more sophisticated studies where sub-centres are identified by analysing mobility flows, such as Autoritat del Transport Metropolità (1998) or Burns et al. (2001). Lastly, the study by

EMPLOYMENT DECENTRALISATION IN BARCELONA 3043

Figure 2. Orography of the Barcelona Metropolitan Region. Source: authors’ elaboration using Corbes de nivell map produced by Institut Cartogràfic de Calunya (ICC) and available at the Departament de Medi Ambient (DMA) website (http://mediambient.gencat.cat/cat/el_departament/cartografia/docs/cartografia_referencia.jsp).

Figure 3. Transport infrastructure in the Barcelona Metropolitan Region. Source: authors’ elaboration using Xarxa Principal de Carreteres graph produced by Institut Cartogràfic de Calunya (ICC) and available at the Departament de Medi Ambient (DMA) website (http://mediambient.gencat.cat/cat/el_departament/cartografia/docs/cartografia_referencia.jsp).

3044 MIQUEL-ÀNGEL GARCIA-LÓPEZ AND IVAN MUÑIZ

Figure 4. Gross employment density in the Barcelona Metropolitan Region, 1986. Source: authors.

Figure 5. Gross employment density in the Barcelona Metropolitan Region, 2001. Source: authors.

Muñiz et al. (2003) defines a sub-centre to be a municipality presenting a maximum local population density.

In the light of the very few studies that consider the question, it is surprising how conclusively the polycentric character of the

EMPLOYMENT DECENTRALISATION IN BARCELONA 3045

BMR tends to be stated. The already long list of studies focusing on identifying sub-centres that has appeared over the past 20 years in the main specialist journals does not appear to have influenced the applied research. The only exception is the study by Muñiz et al. (2008) which adapts the threshold methodology pro-posed by Giuliano and Small (1991) and iden-tifies nine employment sub-centres in 2001. However, the aim of the study is not to test the employment polycentric model. Instead, the authors study the effect of employment sub-centres on population density and its evolution between 1991 and 2001.

4. Methodology

4.1 Employment Centre Identification and Spatial Structure Changes

Because the objective of this study is to assess changes over time in the level of polycentric-ity in the BMR, the proposal by Muñiz et al. (2008) has been adopted to characterise the BMR’s employment spatial structure through the identification of its main employment centres. Although numerous methods have been developed, the threshold methodology is one of the most used due to its objectivity and replicability (see Giuliano and Small, 1991; Song, 1994; Cervero and Wu, 1997; Forstall and Greene, 1997; McMillen and McDonald, 1997, 1998; Bogart and Ferry, 1999; Anderson and Bogart, 2001; Shearmur and Coffey, 2002; or Giuliano et al., 2007; among others). The method defines a minimum level of density and a minimum amount of employment: an employment centre is a location with a density level greater than the density cut-off and with an amount of employment greater than the employment cut-off. As McMillen and Lester (2003) noted, this method has advantages when comparing results for a single city over time, mainly the use of the same cut-offs for different years. However, if we use numerical thresholds and we study the city in a period of intense growth of employment, then there

is a trend to identify an excessive number of employment centres. As Muñiz et al. (2008) noted, we can avoid this problem using statis-tical thresholds, which are more flexible and correct the inflationary effect on the number of centres identified.

Therefore, we apply the statistical thresh-old methodology proposed by Muñiz et al. (2008), but following a temporal point of view, thus analysing the employment spatial structure over time. Following the Muñiz et al. (2008) study, the BMR’s central business district (CBD) consists of the municipality of Barcelona and its 12 adjacent municipalities in a continuous built-up area. As a result, we identify employment sub-centres for 1986 and 20014 as municipalities with an employ-ment gross density (Di, t) greater than or equal to the average density of the BMR (D̄BMR, t) and with a level of employment (Ei,t) greater than or equal to 1 per cent of the BMR total (EBMR, t). These values generate a reasonable number of sub-centres for each year considered

Di, t ≥ D̄BMR, t

Ei,t ≥ 1% EBMR, t

In the case of the Barcelona metropolitan region, the main weakness of the exercise may be the fact that employment data only exist at a municipal level. If data were available at a more local spatial scale, such as census tracts, we would be able to identify more precisely the polycentric model followed by employment. In this sense, for example, if two adjacent municipalities are identified as sub-centres, with our data we cannot know whether their employment is located along a main road that link both municipalities, thus forming a unique sub-centre, or whether they are two historical employment centres with high-density levels and clearly separated one from another. In our analysis, we assume the latter location pattern.

Once employment centres are identified, we follow the studies by Gordon and Richardson (1996) and Giuliano et al. (2007) and compute

3046 MIQUEL-ÀNGEL GARCIA-LÓPEZ AND IVAN MUÑIZ

the amount and the metropolitan share of the employment located in the CBD, the employ-ment sub-centres and other towns in 1986 and 2001. These values and their variation in the 15 years provide us a first insight into the polycentricity vs scatteration comparison: in a context of employment decentralisation and deconcentration, polycentricity is strengthened when sub-centre values increase, whereas scat-teration is the dominant trend when other town values rise.

4.2 Employment Centre Influence and Spatial Structure Changes

The spatial structure of a city is “the degree of spatial concentration of urban population and employment” (Anas et al., 1998, p. 1431) and “an abstract or generalized description of the distribution of phenomena in geographi-cal space” (Horton and Reynolds, 1971, p. 36). In other words and applied to employment, it is the number and importance of employ-ment centres and the pattern of employment location.

This is precisely the point of view of the new urban economics (NUE) models when characterising polycentricity: it is not only employment centres that matter, but also their influence on the pattern of location and density of non-central employment. In other words, employment centres, besides concentrating a large amount of employment, also structure the location of employment outside them. Specifically, it is expected that employment density decreases as we move further away from the CBD and employ-ment sub-centres because the access to the agglomeration economies generated by them is limited by distance: the greater the distance, the lesser the real access to these agglomera-tion economies and, therefore, the bid rent for the land and density.

The ‘de-structuring’ hypothesis or an increasingly random location of employment might be the result of an intense reduction of transport cost and/or the disappearance

of the agglomeration economies due to an increase in congestion costs.5 In both cases, the influence of employment centres, that is, their capacity to structure employment location would decrease over time until its disappearance.

In order to measure the influence of employment centres, we estimate a polycen-tric density function with the same goal as the traditional monocentric density function: to explain the value of employment density in each intrametropolitan zone (in our case municipalities) depending on its location, on its distance to the structuring elements of the city, mainly employment centres. The esti-mated coefficients of these distances are the so-called density gradients6 and their values and significances measure their structuring capacity, their influence.

For the case of a polycentric spatial struc-ture, McDonald and Prather (1994) show various examples of density functions. In our case, we adopt the most commonly used7

InD(dCBD, dSUB, dINF) = α0 + α1dCBD + (1)α2d-1

SUB + α3dINF + e

in which, D(dCBD, dSUB, dINF) is the gross density of employment at a distance8 dCBD from the CBD,9 at a distance dSUB from the sub-centre and at a distance dINF perpendicular from the

closest route infrastructure;10 α1 is the density gradient associated with the distance to the CBD; d-1

SUB is the inverse11 of the distance to the nearest sub-centre,12 α2 its corresponding density gradient;13 α3 is the density gradient associated with the infrastructure; and e is the error term with the usual properties.

From a static point of view, the interpreta-tion of the CBD’s and infrastructure coef-ficients can be performed directly: a negative (positive) coefficient shows a decreasing (increasing) density pattern when we move further away from these structuring elements. Conversely, the reading of the estimated coef-ficient for the inverse of the distance to the nearest sub-centre is the opposite: a positive

EMPLOYMENT DECENTRALISATION IN BARCELONA 3047

(negative) gradient is related to a density pat-tern that decreases (increases) with distance. In all cases, a significant decreasing density pattern would verify the influence of the related structuring element on the location of non-central employment. On the other hand, an increasing density pattern and/or a non-significant gradient would show the lack of influence.

From a temporal point of view, an increas-ing (decreasing) gradient related to a decreas-ing density pattern would show an increase (decrease) of influence of the structuring element. On the other hand, a decreasing significance of these gradients would show the emergence of a more unstructured and amorphous location model. In this sense, in a context of employment decentralisation affecting the CBD, if the polycentric model was strengthening, then the sub-centre density gradient and its significance would increase. However, if a more scattered model was emerging, the gradient would lose signifi-cance and value.

5. Decentralisation and Polycentricity in the BMR

5.1 Employment Decentralisation in the BMR, 1986–2001

Table 1 shows data that reveal the changes in the model for the location of economic activity between 1986 and 2001. Over these

15 years, employment grew by 71.4 per cent, the surface area of transport infrastructure doubled, with the average weighted distance from the job location to the closest route of access falling notably. By contrast, the average weighted distance from the place of work to the CBD centroid increased by 1.28 km (some 13 per cent) and the value of the Gini index applied to municipal employment fell, which indicates a trend towards a more decentralised and less concentrated employment location.

During the period under consideration, the number of jobs in the CBD grew by 52.1 per cent. This is a very significant expansion, occurring after a long period of recession and economic adjustment. Despite this important growth in absolute terms, employment grew with greater intensity in the BMR as a whole, whereas by comparison the CBD declined in importance, going from 64.8 per cent of jobs to 57.5 per cent. We are therefore faced with a relative decentralisation of employment (Table 2).

The 12 municipalities adjacent to Barcelona underwent heavy expansion from the 1950s onwards, as they were originally rural villages which rapidly became dormitory towns and were developed with massive tower blocks for the immigrant population arriving from the south of Spain attracted by the industrial expansion in Barcelona. This dormitory city status has been remedied over the years by applying a policy of providing services and

Table 1. Main characteristics of employment in the BMR, 1986–2001

1986 2001 1986–2001

Employment 1 063 000 1 822 000 +759 000 (71.4)Infrastructure land (hectares) 3 155 11 040 +7 885 (250)Employment decentralisation (average weighted distance to the centre of Barcelona) (km) 9.82 11.10 +1.28 (13)Employment deconcentration (Gini index) 0.86 0.81 —Average weighted distance from the 3.71 2.64 -1.07 (-28.8)employment to the closest access route

Note: percentages are shown in parentheses.

3048 MIQUEL-ÀNGEL GARCIA-LÓPEZ AND IVAN MUÑIZ

Table 2. Employment decentralisation and polycentricity in the BMR CBD, 1986–2001

1986–2001 1986 2001 (percentages) Job ratio 2001

CBDa 689 385 (64.8) 1 048 400 (57.5) 52.1 1.04Barcelona 525 412 (76.2) 763 093 (72.8) 45.2 1.22Other central towns 163 973 (23.8) 285 307 (27.2) 74.0 0.75Badalona 33 001 (20.1) 54 582 (19.1) 65.4 0.69Cornellà de Llobregat 13 007 (7.9) 27 608 (9.7) 112.3 0.85Esplugues de Llobregat 12 010 (7.3) 15 304 (5.4) 27.4 0.81L’Hospitalet de Llobregat 40 632 (24.8) 66 216 (23.2) 63.0 0.70Montgat 1 596 (1.0) 2 143 (0.8) 34.3 0.59El Prat de Llobregat 15 639 (9.5) 31 581 (11.1) 101.9 1.22Sant Adrià del Besòs 7 260 (4.4) 10 461 (3.7) 44.1 0.90Sant Boi de Llobregat 12 052 (7.3) 23 300 (8.2) 93.3 0.74Sant Feliu de Llobregat 6 507 (4.0) 12 777 (4.5) 96.4 0.71Sant Joan Despí 6 214 (3.8) 12 637 (4.4) 103.4 1.01Sant Just Desvern 4 460 (2.7) 9 610 (3.4) 115.5 1.60Santa Coloma de Gramenet 11 595 (7.1) 19 088 (6.7) 64.6 0.44

a Percentage of employment compared with the total for the BMR in parentheses. In all other cases, the percentage of employment is compared to the total for the CBD in parentheses.

Table 3. BMR employment subcentres, 1986–2001

1986 1991 1996 2001

6 6 7 9Granollers, Mataró Rubí, Cerdanyola del Martorell (emerging) Sant Cugat del Sabadell, Terrassa, Vallès (emerging) Vallès (emerging) Vilanova i la Geltrú Vilanova i la Geltrú Vilanova i la Geltrú (declining) (emerging)

the location of industrial estates and shopping centres which have significantly increased the number of jobs. Between 1986 and 2001, the growth in employment was more intense in the towns adjacent to Barcelona than in the city of Barcelona itself, in such a way that the trend towards decentralisation in the BMR is replicated to a lesser extent in the CBD itself, although at present only 3 of the 12 munici-palities have a job ratio higher than 1, which reflects the on-going importance of their spe-cialisation in residential functions (Table 2).

5.2 Employment Spatial Structure in the BMR

The results obtained applying the employ-ment sub-centre identification methodology

(Table 3 and Figure 6) confirm the existence of a polycentric-type spatial structure, in both 1986 and 2001. This polycentricity is based on a huge CBD and a group of employment sub-centres (between 6 and 9 depending on the year of identification).

The sub-centres14 have an average surface area that is 65 per cent larger than the region’s municipalities as a whole (3300 hectares as opposed to 2000 in 2001) and a land surface area that is 3.2 times more developed (1100 hectares as opposed to 350 in 2001). As a whole, they present a population, number of jobs and density conditions that are also higher. The sub-centres identified can be grouped into two categories. The first group consists of medium-sized towns, which in

EMPLOYMENT DECENTRALISATION IN BARCELONA 3049

the past were to some extent autonomous from Barcelona. They cannot be classified as dormitory or satellite towns because they have a high job ratio. They are towns that follow a secondary-centre logic in a Christallerian context and which are currently fully integrated with the other towns in the BMR (Sabadell, Terrassa, Mataró, Vilanova and Vilafranca). The second group consists of employment sub-centres that have arisen from decentralisation rather than integration (Martorell, Cerdanyola, Sant Cugat, Rubí, Granollers).

5.3 Comparing the Degree of Scatteration with that of Polycentricity

Regarding the polycentricity vs scatteration comparison, according to the data shown in Table 4, in 1986 64.8 per cent of employ-ment was concentrated in the CBD, 14.8 per cent in the sub-centres and the rest—i.e. 20.4 per cent—in a large number of smaller towns. Taking only the sub-centres identi-fied in 1986 as the baseline, the percentage of jobs in the CBD in 2001 had fallen to

57.5 per cent, while in the sub-centres it had fallen to 14 per cent and it had risen to 28.5 per cent of employment in the other towns (col. (2)). Despite employment increasing in nominal terms in all geographical areas (col. (3)), these provisional results appear to show that scatteration is increasing at the expense of polycentricity. However, when the sub-centres identified in 2001 are included, the weight of the sub-centres increases to the extent that they account for 18 per cent of employment, and that of other towns falls to 24.5 per cent (col. (5)). When we compare the increase in employ-ment that took place in the sub-centres identified in 1986 with that of those identi-fied in 2001 (cols (3) and (6)), significant changes in the polycentricity model become apparent. Not only has the number of sub-centres increased, but the increase in employment in the new sub-centres has also been notably more intense than in the older ones. This is possibly due to the latter hav-ing reached a maturity which in some cases has led to a decentralisation of employment

Figure 6. Employment sub-centres in the BMR.

Source: authors.

3050 MIQUEL-ÀNGEL GARCIA-LÓPEZ AND IVAN MUÑIZ

which has become concentrated on their own outskirts.

The rates of growth in the number of jobs, and the variation in the percentage of jobs in each spatial area, show that the weight of the sub-centres has increased, although not to the same extent as the employment distrib-uted among the other towns (excluding the CBD). These data confirm that polycentricity and scatteration take place at the same time, although the dynamism of employment in more dispersed areas is more intense than in sub-centres. However, the important dyna-mism of the new sub-centres (those identified in 2001 but not in 1986) cannot be ignored. In fact, employment in these towns has increased at a rate of around 200 per cent (a higher rate of growth than that of employment located in ‘other towns’), as it increased from 23 955 jobs in 1986 to 51 800 in 2001.

5.4 Is an Unstructured and Random Location Model Emerging?

Is the employment location model in the BMR increasingly unstructured? Does employment tend to locate in an increasingly random way without being affected by the structuring elements of the city? To answer these two versions of the same question, we estimate equation (1). As mentioned earlier, in doing so we measure the influence of employment centres on the pattern of location and density of non-central employment. We estimate by ordinary least squares and, in order to correct possible problems of heterocedasticity in the cross-section sample, the standard errors and the covariance matrix have been calculated using White’s (1980) method.

The results obtained using the sub-centres identified in 1986 and 2001 as the baseline, Table 5, show estimated gradients α1, α2 and

Table 4. Changes in polycentricity in the BMR, 1986–2001: share and growth

Sub-centres identified in 1986: 6 Sub-centres identified in 2001: 9

1986 2001 1986–2001 1986 2001 1986–2001 (1) (2) (percentages) (4) (5) (percentages) (3) (6)

CBD 689 385 1 048 400 52.1 689 385 1 048 400 52.1 (64.8) (57.5) (64.8) (57.5)Sub-centres 157 063 255 898 62.9 181 018 327 698 81.0 (14.8) (14.0) (17.1) (18.0)Other towns 216 835 518 521 139.1 192 880 446 721 (20.4) (28.5) (18.1) (24.5) 131.6

Note: percentages are shown in parentheses.

Table 5. Changes in polycentricity in the BMR, 1986–2001: changes in gradients

Sub-centres identified in 1986: 6 Sub-centres identified in 2001: 9

1986 2001 1986 2001 (1) (2) (3) (4)

α0 1.627*** (5.45) 2.652*** (10.90) 1.605*** (5.09) 2.590*** (10.01)

α1 -0.058*** (-5.65) -0.062*** (-7.09) -0.056*** (-5.40) -0.060*** (-6.80)

α2 1.874*** (5.23) 1.722*** (6.15) 1.338*** (3.10) 1.380*** (4.16)

α3 -0.389*** (-5.70) -0.427*** (-6.27) -0.394*** (-5.83) -0.430*** (-6.39)

R̄2 0.4919 0.6178 0.4831 0.6145

Note: *** significant at the 0.01 level.

EMPLOYMENT DECENTRALISATION IN BARCELONA 3051

α3, that are significant in all the years. The negative signs for α1 and α3 indicate that the density of employment decreases with distance to the CBD and the closest route infrastructure; and the positive sign of α2 implies that density also falls as the nearest sub-centre becomes more distant. The CBD and sub-centres therefore determine the employment location pattern and its density conditions.

From a longitudinal point of view and taking the sub-centres identified in 1986 as the starting-point (cols (1) and (2)), CBD’s and infrastructure gradient and significance increase over time, showing an increase in their structuring role. On the other hand, the value of the sub-centre gradient falls, whereas its significance level increases. This seems to show that, although in 2001 these sub-centres had lost influence on the location of non-cen-tral employment (decreasing gradient), they kept on structuring the employment location outside centres (increasing significance). If we consider the sub-centres identified in 2001 as the baseline (cols (3) and (4)), an increasing gradient and significance verify that employ-ment sub-centres, especially the new ones, acted as a magnet for other employment.

As a result, it seems that the polycentric model has been strengthened with the emer-gence of new sub-centres between 1986 and 2001, but also with a greater influence on the location of non-central employment. What is more, despite the undergoing decentralisation process, the CBD reinforces its structuring role. Finally, transport infrastructure keeps on influencing employment location.

6. Conclusions

At the present time, most large cities in the world are polycentric and, at the same time, they are undergoing processes of employ-ment decentralisation and deconcentration. Gordon and Richardson (1996) argued that polycentricity is just an intermediate stage

between monocentricity and a more unstruc-tured, chaotic and amorphous location model, scatteration. For the case of the Barcelona metropolitan region, this paper has studied the polycentricity–scatteration discussion, analysing the two main predictions of Gordon and Richardson (1996) study: is employment moving from polycentricity to scatteration and is the employment location model increasingly random and unstructured?

The results show that the spatial structure of employment in the BMR changed signifi-cantly between 1986 and 2001. Employment became more decentralised and decon-centrated, as shown by the growth in the average weighted distance to the CBD and the fall in the Gini coefficient respectively. Furthermore, employment in employment centres (CBD and sub-centres) increased less intensively than in the group consisting of the other towns. According to the techniques for analysis that are usually used in studies that attempt to predict whether decentralisation of employment entails increased polycentricity or a growing scatteration, these results would suggest a trend towards scatteration.

However, this research aims to describe the role of sub-centres in the new model of employment location that appears to be pre-vailing. The results suggest that sub-centres continue to have an important role. First, new sub-centres of employment seem to have been created in the 15 years, which does not fit in with the idea that scatteration displaces polycentricity. Secondly, while it is true that employment outside centres has grown more intensively, it is also true that this growth has tended to be concentrated near the sub-centres, as is shown by the increasing density gradient and significance related to employment sub-centres (the nine identified in 2001).

Therefore, the empirical evidence obtained for the case of the BMR allows us to state that: polycentricity and scatteration do not appear to be two alternative models but are in fact complementary; and, the dispersion

3052 MIQUEL-ÀNGEL GARCIA-LÓPEZ AND IVAN MUÑIZ

of employment does not follow an amor-phous model, but is instead structured based on transport infrastructure, the CBD and the sub-centres. As a result, the polycentric model still prevails in 2001 and, moreover, it is strengthened with a greater influence on the location of non-central employment.

From a conceptual point of view, our find-ings show that the influence of employment centres on the location of the employment outside their boundaries needs to be taken into account in order to characterise prop-erly the evolution of the spatial structure. Indeed, most of the previous studies on the polycentricity vs scatteration topic have used census-tract data to identify and characterise more accurately their employment centres. However, the spatial organisation of their non-central settlements and its evolution still remain unexplored. An update of these stud-ies in order to measure the structuring role of their centres might reveal a different spatial trend of their urban forms. Like Barcelona, maybe Los Angeles is not beyond polycen-tricity, as stated by Gordon and Richardson (1996), but is strengthening it, as stated by Giuliano et al. (2007). From a methodologi-cal point of view, our approach provides a well-known tool to study easily this feature of spatial structure in Los Angeles and in other urban realities.

Notes

1. Both studies provide an excellent outline of the spatial extent of agglomeration, the contribution of sectors and the types of external economies.

2. Population and employment data come from the 1986 and 2001 population censuses, which are produced by the Instituto Nacional de Estadística (INE).

3. Calculated using the 2002 Mapes d’Usos del Sòl de Catalunya, produced by the Institut Cartogràfic de Catalunya (ICC) and available at the Departament de Medi Ambient (DMA) website (http://mediambient.gencat.cat/cat/el_departament/cartografia/fitxes/).

4. In fact, we also identified 1991 and 1996 employment sub-centres, as shown in Table 3. However, we only focus on the 1986 and 2001 results.

5. Both explanations depend on the kind of agglomeration economies considered. If they are related to face-to-face contacts, the second would apply. If they are related to access to a harbour from which goods are exported, then the first explanation would apply.

6. The density gradient expresses the percentage change in density due to an increase in the distance.

7. In its non-linearised form, this function is a multiplicative exponential—i.e. it is the product of different exponentials in which, for each one, specification is made of a negative relation between density and distance for each of the cities considered, CBD and the nearest sub-centre. Its linearisation is performed to facilitate its estimation.

8. The calculation of distances is carried out using a GIS software that obtains the centroids of each municipality. The co-ordinates of these centroids are used for each municipality to calculate their euclidian distances with respect to the CBD, the sub-centres and the infrastructure.

9. In our case, we use distance to Barcelona.10. In order to control the effect of municipal

accessibility to the region as a whole, the distance to the closest infrastructure route has been included, something which has decisively affected the pattern of urban development and the location of employment, as well as the distance to the CBD.

11. Using an inverted distance enables problems of multicollinearity to be removed (McDonald and Prather, 1994). Other works which use this synthesis variable are those by McMillen and McDonald (1998) and McMillen and Lester (2003).

12. The use of the nearest sub-centre instead of each sub-centre is due to the limited number of observations (municipalities), which generates problems in estimating the individual gradients for the physically adjoining sub-centres. On the other hand, imposing a unique gradient for all sub-centres means losing individualised information for each of them.

EMPLOYMENT DECENTRALISATION IN BARCELONA 3053

13. Note that working with a direct distance for the CBD (Barcelona) and an inverted distance for the nearest sub-centre entails acknowledgement that the spatial influence of the CBD is greater than that of the sub-centres.

14. For more information regarding the BMR’s employment sub-centres, consult Muñizet al. (2008).

Acknowledgements

The authors are grateful to three anonymous referees and to the Editors for their very helpful comments on an earlier version of the paper. The last revision was finished when the first author was doing research at the School of Policy, Planning, and Development (University of Southern California). Thanks to Christian L. Redfearn, Genevieve Giuliano, Peter Gordon, Scott Burgess and Marta Marot for support-ing this stay. Financial support for the stay was given by the Ministerio de Ciencia e Innovación (Spain) through “Ayuda de estancias de movili-dad posdoctoral en el extranjero, incluidas becas MICINN/Fulbright y Cátedras Príncipe de Asturias 2008–2009”.

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