Demography, Vol. 32, No.1, February 1995

Estimates of Early Twentieth-CenturyU.S. Homicide Rates: an EconometricForecasting Approach*

Douglas Lee EckbergDepartment of SociologyWinthrop UniversityRock Hill, SC 29733

Bureau of the Census death registration records, as reported in Mortality Statistics,are a primary source for early twentieth-century U.S. homicide statistics. Those dataappear to show a massive rise in homicide during the first decade of the century, witha continuing increase through 1933. This increase is quite at variance with the trendaway from violence in other industrialized societies. During the first one-third of thecentury, however, death registration was incomplete; it occurred only in an expanding"registration area" that was composed, in the earlier years, primarily of states withtypically low rates of homicide. Further, in the first decade of the century homicideswithin the registration area often were reported as accidental deaths. As a result,apparent increases in rates of homicide in the United States between 1900 and 1933may be illusory. I use a two-step process to address these problems. Drawing oninternal evidence and commentaries in early volumes of Mortality Statistics, I useGLS regression to estimate the prevalence of undercounts. Then I create a series ofGLS models that use registration area data to estimate early twentieth-century nationalrates. These estimates call into question the extent of homicide change early in thecentury.

Did the United States experience a surge of homicide early in this century? Variousscholars answer "yes," but if this is true it is a curious phenomenon. Research on otherindustrial societies shows a long-term downward trend in murder that proceeded well intothe twentieth century. This once was called a "civilizing" trend (Lane 1968), a term for aprogressive increase in emotional control accompanying modernization, which led (amongother things) to a decrease in interpersonal violence (Elias [1939] 1978). The civilizing"thesis" fits both the historical data from European societies and anthropological findingson violence in horticultural and agrarian societies (e.g., Bloch [1940] 1961; Given 1977;Hanawalt 1979; Huizinga [1924] 1954; Sorokin 1937). Since the 1960s, however, violencehas increased somewhat, and some theorists now argue that rates overall follow a long-termU-curve (GUIT 1989; Lane 1980).

The U.S. picture differs from Europe's in two ways. First, in countries such as

* Direct all correspondence to Douglas Lee Eckberg, Department of Sociology, Winthrop University, RockHill, SC 29733. Earlier versions of this paper were presented at the annual meetings of the Southern SociologicalSociety, held in Atlanta in April 1991; the Southern Demographic Association, held in Charleston, SC in October1992; and the Homicide Research Working Group. held in Atlanta in June 1994. I thank Kim Kryter for early help,and Jack Tucker, Jon Marx, Daryll Parker, Margaret Zahn, and Jim Bentley. and the anonymous reviewers.

Copyright © 1995 Population Association of America

1

2 Demography, Vol. 32, No.1, February 1995

England the twentieth-century increase in violence began in the 1960s, but in the UnitedStates it apparently began very early in the century. Second, the increase in England wasvery modest in comparison with the long-term decline, but the United States appears now tohave murder rates far above those at the tum of the century.

U.S. violence research has relied primarily on police arrest and indictment records(Ferdinand 1967, 1972; Hindus 1980; Lane 1979, 1986; Powell 1966). Although thesesuggest a rise early in the century, the data are scattered and are confined principally toeastern and midwestern cities. The most ambitious study, Monkkonen's (1981) analysis ofpolice reports from most of the largest nineteenth-century U.S. cities, found a large increasein the homicide arrest rate (per 100,000 population) from 1890 to 1920. The data, however,often were incomplete, were missing for whole years, or were incommensurable acrossjurisdictions.

This issue has long been disputed. In 1925 Hoffman used homicide statistics from 28large U.S. cities to argue that the rate of homicide had effectively doubled since 1900, butSutherland (1925) employed evidence from 61 large cities and from the states then in the"death registration area" to argue that homicide had not increased greatly. Brearley (1932)later concluded that Sutherland was correct and that two factors had caused an apparentincrease in homicide: improving accuracy in reporting, and changes in the composition ofthe registration area. Within "comparable areas" the homicide rate had not increasednotably, but as the registration area grew it took in states with "appreciably" higherhomicide rates than the states that had composed it originally.

At least some of the early increase in violence was an artifact of policing practices,which changed from underreporting homicides to "over charging" offenses by "one or twodegrees" (Lane 1979; 1989). In Philadelphia much of the apparent increase was caused bya transitory policy of counting deaths by automobile accident as homicides (Weiner andZahn 1989). In addition, a "dark figure" of unreported murders decreased greatly. As aresult, researchers now disagree about the existence of a "homicidal crime wave" (Gurr1989; Lane 1989; Zahn 1989).

DEATH REGISTRATION DATA AND THE STUDY OF HOMICIDE

I propose to use death registration data to investigate the homicide increase early in thecentury and, more generally, the twentieth-century history of U.S. homicide. These datasuffer the problems discussed above, but the problems are amenable to treatment witheconometric forecasting techniques that will allow both trend analysis and accurateestimation of annual homicide rates for the entire nation. There are several reasons to usesuch data as alternatives, or supplements, to law enforcement data. With the exception ofMonkkonnen's (1981) cities, the registration area included a much greater proportion of theU.S. population than one finds in urban arrest data. By 1900 the states in the area alreadyincluded 26% of the U.S. population. Also, because these states included both rural andurban areas, the "urban bias" of arrest data is avoided. Admission to the registration arearequired achievement of uniform standards, so the data should be more comparable than arepolice reports. Finally, the death registration data should not include deaths by automobileaccidents among homicides; by 1906 these already were being tabulated as a specificcategory of accidental death.

Beginning with a small group of states and cities in 1880, the death registration areaexpanded as jurisdictions developed registration procedures that met mandated criteria ofreliability and completeness. By 1933 it encompassed the entire nation. Annual publicationof deaths from the area began in 1906 with the first volume of Mortality Statistics, whichcovered the period 1900-1904. Homicide was one major subdivision of death "by external

20th Century U.S. Homicide Rates 3

causes" or "by violence" (hereafter "violent death"); the other two were suicide andaccidental death.

Figure 1 shows annual crude rates of homicide for states in the registration area. Therates increase dramatically until 1933 (when full U.S. death registration was achieved), andfollow a U-curve thereafter. The combination of pre- and post-1933 figures yields thepicture of a general twentieth-century rise: between 1900 and 1933 rates increase by a factor

Rate per 100,000 Population

12 r-------------------------------,

\Lower line is reported rate fordeath registration states.

6

4

8

Upper line is estimated U.S.rate and c.i. (see text).

10 / / 1933 begins completeU.S. death registration.

2

898070605040'302010

0LW-.L.U..L.U..L.U..u..Jc.u...LW-.L.U..L.U..L.U..u..J...J....L..LW-LW-.L.U..L.U..u..J...J....L..LW-LW-.L.U..L.U..u..J...J....L..LW-.L.U..J....L...L.L.U..u..Ju....L..L..L..L..U

1900

Year3 To nearest tenth point; includes 95% confidence interval for years before complete registration

Figure 1. U.S. Homicide Rates, 1900-19893

4 Demography, Vol. 32, No.1, February 1995

of 5 in the registration-area states (and by a factor of 9 for the whole registration area),because of remarkably low rates for the first decade.

The data before 1933, however, are misleading in two important ways. First, theregistration area did not include a random group of states. As Brearley suggested, early inthe century it disproportionately included states with low rates of homicide. Indeed, for thefirst two decades of full national data, the set of registration states of 1900 typicallyexperienced homicide rates less than half the national rate (see Figure 2). Second, during thefirst decade of reports homicides were underreported within the registration area, perhapsextensively. This problem was discussed at length in the early volumes. Together thesepoints imply that published homicide rates initially were substantially lower than actualnational rates, and then progressively converged on national rates.

Although this lack of representativeness has not gone unnoticed, no one has publishedefforts to adjust for it. Researchers have issued warnings, have refused to employ early data,or simply have used the data as published (e.g., Archer and Gartner 1984; Brearley 1932;Henry and Short 1954; Holinger and Klemen 1982; Iskrant and Joliet 1968; Klebba 1981;Zahn 1980). According to Vital Statistics-Special Reports (1956:479) registration-areahomicide rates were "approximations to complete national rates, and general comparisonsover a long period of years can be made," but such comparability has not been establishedand almost certainly does not exist. The use of these data may have serious consequencesfor the historical picture of murder in the United States and for studies that use earlyregistration-area data in quantitative analysis.

ECONOMETRIC "FORECASTING" OF HOMICIDE RATESIn principle, it should not be difficult to derive estimates of U.S. homicide rates for the

period 1900-1932, using data from sets of registration-area states and the application of aRates per 100,000 Population

Slop 23 (Tolol U.S. Rolol

IStop 18

\

10 --------------------""':":'-:-:-::-:-"':""::'~:_:__:__---

4

6

6

2-----------------------------

I 1 I I I I I I I I I I

1907 1910 1915

I I I

1920

I I I I I I I I I I I I

1925 1930

I I I I I

1935

I I I

1940

I I I I I

1945

I I I I

1950

Year

a Selected steps are labeled.Figure 2. Homicide Rates for All Steps, 1907-1950'

20th Century U.S. Homicide Rates 5

well-known regression-based econometric forecasting technique (Abraham and Ledolter1983:ch. 2). In the general case, one uses a least-squares procedure to determine a purelypredictive relationship between two time-series variables, then applies the resulting interceptand slope coefficients to values of the exogenous (x) variable in situations where the valueof the endogenous (y) variable is unknown, to estimate the values of y.

In the present case, data are annual crude homicide rates for the United States and forsets of states from the registration area. Homicide rates for some sets of states are availablefor every year in the century; for the entire United States they are available beginning in1933. I regress national homicide rates across rates for a set of states, using annual rates for1933-1950, to obtain

HOMus = a + (b x HOMREG STATES) + c (1)

(2)

where HOMus is the U.S. homicide rate, HOMREG STATES is the homicide rate for a set ofregistration-area states, a is the intercept, b is the slope, and c is the error term. Given this,for any given year in which one knows HOMREG STATES but does not know HOMus, onecan easily calculate an estimate of the latter. Confidence intervals can be calculated from

S2p

= S2 [1 + .!. + (Xl + 1 - Xl]T I (x, - xl

t

where S2p is the forecast variance, S2 is the sample variance (standard error of the estimate),Xl + 1 is the postsample value of x, and T is the size of the sample of years (Abraham andLedolter 1983). Technically, this equation forecasts (or "backcasts") national homiciderates.

Because positive autocorrelation can seriously inflate R2 in time- series models (seeHanushek and Jackson 1977), I use generalized least squares (GLS) regression. Thisprocedure costs degrees of freedom, which must be minimized because of the small numberof years in the series. Therefore I employ Yule-Walker (two-step, full-transform) equations.

ISSUES IN ESTIMATING NATIONAL HOMICIDE RATES FROMREGISTRATION-AREA DATA

In employing this strategy, one must consider three issues. 1) Models based on thesmall number of states available in the earlier years could have large error terms, andtherefore lack precision. 2) The strategy requires extrapolation of linear relationships fromone time period to another. If relationships change greatly, models may yield biasedestimates. 3) Criteria for the categorization of "homicides" may change.

The first issue can be treated empirically: reliable estimates will have large R2s andsmall standard errors. As will be shown, even the weakest models employed below showsubstantial predictive power. This is not surprising, because data from states are notindependent of national data, but exist in a part/whole relationship; even the earliest set ofstates accounted for one-quarter of the U.S. population.

The second issue is more problematic. Because linear relationships change over time,forecasting usually is used to predict values of a variable at a time period close to that inwhich the equation was estimated. In the extreme case I "forecast" a homicide rate 33 yearsaway from such a period (that is, I estimate rates for 1900 on the basis of a relationship thatholds for 1933-1950). Therefore estimates for the earlier years should be viewed with

6 Demography, Vol. 32, No.1, February 1995

caution. Even so, I provide justification for accepting these estimates as substantially closerto the true figures than are the published figures.

The third issue does not concern changes in established rules for the registration of adeath as "homicide." Categorization changes in the International Classification of Diseaseshave had little effect on homicide reporting (Klebba 1981), and vital statistics figures onhomicide appear to be quite reliable, at least since the point of complete registration (Cantorand Cohen 1980). Rather, the problem concerns undercounts caused by inadequate qualitycontrol; this was a serious problem during the first decade of registration, when bothmurders and suicides often were tabulated as "accidents" because insufficient informationwas forwarded by local authorities. Addressing this problem requires information on sourcesand on amounts of undercount, which comes from Mortality Statistics itself. To resolve thelatter issues, one must understand the history of U.S. death registration.

STEPS IN DEATH-REGISTRATION REPORTING

It is important to recognize the changing composition of the registration area. From oneyear to the next it included a nonrandom, shifting (usually growing) set of states and cities.To generate estimates of national homicide rates, one needs data from comparable areas,from which data are available both before and after the achievement of complete U.S. deathregistration. Accordingly, homicide registration can be divided into 23 "steps," as shown inTable I.

A "step" is the full set of states included in the registration area at anyone time. "StepI" is the set of II states (actually 10 states and Washington, DC) in the registration areafrom 1900 through 1905. Tables in Mortality Statistics reported the number and rate ofhomicides by state; Step I is the smallest and earliest set of such states.

With two exceptions (see Table I), each new step added a state or states to thosealready in the registration area. Therefore each was a "step" toward complete registration."Step 2" refers to the Step I states plus California, Colorado, Maryland, Pennsylvania, andSouth Dakota, which first were included in 1906. Step 23 is the set of all the states, orcomplete national death registration. In the two exceptions, a state previously included inthe registration area (South Dakota and Georgia) was removed for some time because ofinadequate compliance.

I do not use data from registration-area cities in states outside the registration area.Until 1921 the tables for individual cities did not show the number of homicides, butcombined them with accidental deaths in a category initially titled "Violent Deaths (SuicideExcepted)." After 1937, city deaths came to be published by decedent's place of residencerather than by the old criterion of place of occurrence. This change altered the homicidecounts for many cities, and could produce biased estimates if the counts were used inregression.

LONG-TERM DIFFERENCES IN HOMICIDERATES AMONG STEPS

If early registration-area homicide rates are artificially low, then later steps will havehigher rates than earlier ones. Figure 2 illustrates this point by graphing rates of homicide inall existing steps yearly for 1907-1950 (though excluding South Dakota and Georgia beforethose steps in which they entered the registration area permanently). The steps weresequential and cumulative: earlier steps remained in existence as later ones formed.

20th Century U.S. Homicide Rates

Table 1. Cumulative Death Registration States, 1900 to Present

7

Step

12345

6789

1011121314151617181920212223

Year(s)

1900-190519061908190919101911-191219131914-191519161917

191819191920192219231924192519261927192819291930-19321933-

States

CT, DC, IN, MA, ME, MI, NH, NJ, NY, RI, VTadd CA, CO, MD, PA, SDadd WA, WIadd OHadd MN, MT, UT; remove SDa

add KY, MOadd VAadd KSadd NC, SCadd TN

add IL, LA, ORadd DE, FL, MSadd NBadd GA, ID, WYadd IA

add NDadd AL, WV; remove GAbadd AZadd ARadd GA, OK

add NM, NVadd SDadd TX

Source: Mortality Statistics, various years.a SD was removed until 1930; NC was shown on Mortality Statistics tables, but until 1916 data

came only from cities.b GA was removed until 1928.

Figure 2 is complex because it graphs 23 curves, one for each step. Still, severalclosely related points are immediately obvious. Rates for consecutive steps are not merelydifferent, but follow a clearly ascending pattern: later steps have higher rates. This is thecase because (as a rule) the higher a state's homicide rate, the later it was admitted to theregistration area. In 16 of the 22 years in which a new step was formed, the homicide ratefor the newer step was higher than for the older one, yielding a Kendall's tau of .45 betweenorder of formation and (low) homicide rank. If we use only data for 1933, when all stepsfirst are available, Pearson's r between step number and (low) homicide rank is .98; the rbetween step number and homicide rate is .96 (the corresponding tau is .89 in both cases).

Simply put, registration-area data from different years are not equivalent. Until 1933,annual homicide rates for the registration area essentially represent continual shifts toever-later steps, and so give the false impression of dramatic increases in homicide rates.This impression is an artifact of the shifting itself.

In support of this conclusion, rank orders of rates for steps are almost invariant acrossthe entire half-century period. Although the rates for some groups of steps are extremelyclose to one another and intertwine across the graph (Steps 2-5, for example, shown inFigure 2), those which differ clearly at anyone time never exchange ranks. The U.S. rate(Step 23) is always highest; Step 1 is always lowest.

8 Demography, Vol. 32, No.1, February 1995

Step homicide rates differ greatly, but the timing of changes in rates does not. All stepsfollow the same pattern of increases and decreases in rates, doing so virtuallysimultaneously, and rate gaps between steps are larger in years with higher overall rates.This point suggests very long-term stability in relationships among rates of steps, which ispartly a function of their part/whole nature. In a linear equation that accurately describes therelationship between a step rate and the national rate over a time period, one should findcoefficients that will have predictive utility for a time frame on the order of a half-century;this issue bears further discussion.

CALCULATING ESTIMATES OF NATIONAL HOMICIDE RATES

To derive estimates of national (Step 23) homicide rates, I regress Step 23 rates acrossrates for each of the previous steps, as described above. This procedure generates 22different regression equations. I join the resulting equations to annual homicide rates for theappropriate steps for each year before 1933, to produce the estimates of national rates forthose years. For most of those years, homicide rates from several different steps areavailable (in 1909, for example, one may choose among Steps 1 through 4), so I must selectthe step whose equation most accurately predicts the national rate. To this end, I use theavailable step whose equation yields the smallest standard error of the estimate (results arealmost identical to those obtained by employing the available step with the largest numberof states). This method will not work for the earliest years in the century, however, until theproblem of undercounts is resolved.

THE FIRST-DECADE UNDERREPORTING PROBLEM

Discussion of undercounts throughout the first decade of publication of MortalityStatistics provides important information on scope, causes, and changes. The authors of thefirst volume stated adamantly that "statistics of deaths from suicide, homicide, and variousspecial forms of accident derived from registration records, are incorrect and absolutelymisleading" (Mortality Statistics 1906:lv). Local officials often submitted records of"suspicious" violent deaths without sufficient information to subcategorize them; therefore,said the authors, "they can only be construed as accidental and compiled accordingly,notwithstanding the strong probability that most of them were due actually to either suicideor homicide" (Mortality Statistics1906:1vi; emphasis in original).

Over the five-year period covered by the volume (1900-1904), 97,805 "suspicious"deaths were categorized as accidents, including deaths from fractures, dislocations, burnsand scalds, burning by corrosive substances, drowning, inhalation of poisonous gases, otherpoisonings, gunshot wounds, "traumatisms," "other external violence," and suffocation(Mortality Statistics 1906:1viii). The authors were particularly concerned about 13,850deaths simply titled "fracture"; they believed "there should be no deaths to compile underthis title" (Mortality Statistics 1906:1vii).

The discussion of the problem continued through the 1910 report (though it wasmentioned in passing as late as 1914). By the report for 1905, compilers had begun to returncases to local authorities for correction; consequently compilation was "yearly improving inaccuracy." The authors expected that as a result of this, the rates of homicide and suicideover time would show "apparent" but artificial increases (Mortality Statistics 1907:56-57).

Though officials once had been reluctant to acknowledge homicides and suicides (Lane1979), the report for 1906 suggested that the major problem lay in the fact that deathcertificates did not include a place to specify the causes of violent deaths, and it discussed

20th Century U.S. Homicide Rates 9

a model death certificate that could help to resolve this problem (Mortality Statistics1908:67). Adoption proceeded quickly, and by 1915 almost the entire nation employed the"Standard Certificate of Death" based on the 1908 model (Wilbur 1916:23-26). The reportscontinued through 1910 to mention artificial increases in homicide and suicide rates.

Adjusting Early Homicide Counts

The authors of the reports believed that homicides and suicides were widely mislabeledas accidents in the period 1900-1904, and that reporting of violent deaths was progressivelyrefined until perhaps 1910. We find no indication of a problem in determining whatconstituted either violent death in general or the specific causes. Rather, the problem wassubcategorization by agency of death: was there culpability? If so, was the decedentculpable? If this interpretation is correct, then changes in reporting between 1904 and 1910should have resulted in decreases in the relative rates of accidental death (especially from"suspicious" accidents) and in corresponding increases in the rates of homicide and suicide(by the same causes). Unfortunately, however, one cannot completely trace this process.Homicide was not subcategorized until 1910, by which time the authors clearly believed thatthe underreporting problem had been resolved. In the same year, some types of"suspicious" accidents ceased to be reported in tables.

Three types of suspicious accidental deaths, however, were reported across the entireperiod: those by gunshot, fracture, and poisoning (other than by gas). Changes in the ratesand the relative rates of these types should follow changes in death registration practices.Table 2 traces the rates of violent death, accidental death, homicide, suicide, and the threeforms of suspicious accidental death from 1900 to 1918 in Step 1 (which supplies data bothbefore and after 1910 and forms a standard unit of analysis). Across the period, Panel A ofthis table shows an increase in the overall rate of violent death, and a somewhat lesserincrease for accidental deaths. The former varies from about 88, in 1900 and 1902, toalmost 121 in 1917. The mean changes from 95.4 before 1905 to Ill.5 after 1910. The rateof accidental death rises from a mean of 83.4 before 1905 to 92.1 after 1910. As expected,however, we see a decline in the percentage of violent deaths attributed to accidents. Before1905 the mean is 87.4%; after 1910, 82.6%.

The situation differs substantially for the three types of "suspicious" accidents, all ofwhich decline dramatically. From the highest to the lowest year in the series, death ratesfrom "accidental" poisonings decrease by 55%, from "accidental" gunshots by 62%, andfrom "accidental" fractures by 95%. The wish for no deaths be listed under "fracture" is allbut fulfilled. On the other hand, the suicide rate increases by 64%, and the homicide rate by311%. In view of the discussions in the reports, it is reasonable to infer that these changesare substantially a function of the shift in classification procedures.

The rate of reported homicide rises into its post-191O range in 1907, as do suicide andaccidental gunshot deaths in 1908. In contrast, the death rate by fracture falls sharply in1909. If these changes are taken as criteria, homicides and suicides were reported withreasonable accuracy at least by 1909.

We obtain the same results by using the ratios of homicides to each of the other causesof death; these are shown in Panel B of Table 2. Ratios of homicide to each of the othercauses of death are quite stable both before 1905 and after 1909, with dramatic increasesonly between those years. For most categories, stability is achieved by 1907.

Regression-Based Estimation of Early Step 1 Homicide RatesSeveral researchers suggest that long-term positive relationships exist among rates of

the major forms of violent death in the United States (Gold 1958; Holinger and Klemen

10 Demography, Vol. 32, No.1, February 1995

Table 2. Violent Death from Selected Causes, Step 1, 1900-1918

Panel A: Rates per 100,000 Population

All All"Suspicious" Accidents'

Year Violence Accident Poison Gunshot Fracture Suicide Homicide

1900 87.55 76.19 4.24 2.72 9.31 10.20 1.151901 98.99 87.51 3.84 2.74 9.34 10.33 1.141902 88.05 76.60 4.22 3.00 9.54 10.22 1.231903 98.62 86.32 5.11 3.08 9.84 11.19 1.111904 104.01 90.61 4.93 3.38 9.88 12.09 1.31

1905 102.67 87.20 3.76 2.38 7.92 13.36 2.101906 105.23 89.85 3.86 2.05 7.53 12.51 2.881907 108.93 91.02 3.72 1.70 5.27 13.99 3.921908 103.96 83.33 3.24 1.53 1.73 16.75 3.921909 101.56 82.15 3.20 1.27 0.63 15.94 3.46

1910b 105.70 86.34 2.40 1.35 1.01 15.42 3.931911 114.86 94.82 3.02 1.36 0.64 15.82 4.221912 108.64 89.25 2.96 1.34 0.74 15.29 4.101913 111.89 91.95 3.04 1.59 0.50 15.46 4.481914 107.34 86.73 2.99 1.34 0.83 16.29 4.32

1915 105.76 85.03 2.62 1.34 0.50 16.62 4.101916 114.23 95.28 2.36 1.34 0.93 14.93 4.031917 120.06 101.86 2.38 1.29 0.71 14.54 4.561918 108.33 92.02 2.29 1.27 0.86 12.62 3.69

Panel B: Ratios of Homicides to Deaths from Other Causes

All All"Suspicious" Accidents'

Year Violence Accident Poison Gunshot Fracture Suicide

1900 .0132 .0151 .2719 .4236 .1237 .11301901 .0116 .0130 .2976 .4176 .1225 .11071902 .0139 .0160 .2908 .4093 .1287 .12011903 .0113 .0129 .2179 .3614 .1132 .09951904 .0126 .0145 .2660 .3877 .1326 .1084

1905 .0205 .0241 .5598 .8836 .2658 .15751906 .0273 .0320 .7457 1.4022 .3821 .23011907 .0360 .0430 1.0530 2.3041 .7438 .28001908 .0377 .0470 1.2085 2.5634 2.2581 .23391909 .0341 .0422 1.0833 2.7209 5.5338 .2174

1910b .0372 .0455 1.6350 2.9077 3.9050 .25481911 .0367 .0445 1.3989 3.1054 6.5669 .26681912 .0378 .0460 1.3450 3.0509 5.5081 .26841913 .0400 .0487 1.4715 2.8180 8.8976 .28971914 .0402 .0498 1.4420 3.2151 5.1682 .2650

1915 .0388 .0482 1.5654 3.0632 8.2000 .24651916 .0352 .0423 1.7063 2.9944 4.3388 .26971917 .0377 .0448 1.9160 3.5349 6.4225 .31361918 .0341 .0400 1.6114 2.9182 4.2907 .2924

Source: Mortality Statistics, various years.a "Poison" excludes poison gases. "Fracture" includes "dislocations."bIn 1910, accidental "injuries at birth" ceased to be included among violent deaths. I include

them here to maintain continuity.

20th Century U.S. Homicide Rates 11

1982; Porterfield 1960). With this point in mind, one should be able to use a regressionmodel to determine when an acceptable level of homicide reporting was reached.

I first use GLS regression to determine the relationship between overall rates of violentdeath and rates of homicide. For data I use annual Step 1 rates of the two categories, for theperiod 1909-1918, the first decade for which the data appear to be consistently reliable. Therelationship between the two is expressed as

HOMsTEPI = a + (b x VIOLENCEsTEP1) + c, (3)

where HOMsTEPI is the homicide rate, and VIOLENCEsTEPI is the total rate of violentdeath, in Step 1. The equation is significant and robust, as shown in Table 3 (p<.02,R2 = .58). Because annual rates of violent death in Step 1 are known for 1900-1908, onecan insert them into the equation to obtain point estimates of homicide rates within the stepfor those years.

The change in registration practices should have caused reported homicides to increaseuntil they equaled actual homicides. Therefore the year when the reported homicide raterises to within the 95% confidence interval of the estimated rate will be designated the firstyear of "full" reporting. As shown in Table 3, the reported rate for 1908 (3.92) is actuallyhigher than the estimate (3.79), and the reported rate for 1907 (also 3.92) is well within theconfidence interval (3.41-4.64) for that year. In effect, then, 1907 is the first year of "full"reporting of homicides.

Because I now consider homicide data for 1907 and 1908 to be reliable, I reestimatethe equation, using 1907-1918 data, to increase accuracy (p<.02, R2

= .53). With the newequation I estimate homicide rates in Step 1 for the period 1900-1906. As shown in Table3, a comparison of published figures with point estimates suggests that homicide wasgrossly underreported across the first five years of the century, by an average of 65.5% per

Table 3. Published Homicides, Estimated Real Homicides, and Homicide Undercounts,Step 1: .1900-1908a

Deaths by Recorded Estimated" Estimated"Year Violence Rate Homicides Rate Homicides Rate Undercount

1900 17,475 87.55 230 1.15 621 3.10 62.9%1901 20,164 98.99 233 1.14 736 3.60 68.31902 18,294 88.05 255 1.23 649 3.13 60.71903 20,894 98.62 236 1.11 763 3.59 69.11904 22,461 104;01 283 1.31 825 3.82 65.7

1905 22,590 102.67 463 2.10 829 3.76 44.11906 23,584 105.23 645 2.88 867 3.87 25.61907 24,857 108.93 894 3.92 (4.02) ( 2.5)1908 24,149 103.96 910 3.92 (3.79)

Sources: Mortality Statistics, various years; various censuses of the U.S. population.a Model parameters: Initial parameters were produced by regressing Step 1 homicide rates across

Step 1 violent death rates, 1909-1918 (intercept =-1.07505; slope=0.046812; R2= .584; p<.02).This procedure showed that 1907 and 1908 rates were reasonably accurate. Estimates of 1900-1906Step 1 homicide rates were then produced by using 1907-1918 data (intercept = -0.70873;slope =0.043543; R2= .533; p<.02). Beginning with 1910 data, I include "injuries at birth" amongviolent deaths to maintain continuity with data for 1900-1909.

b To the nearest integer. Estimated homicides = E/RN, where E = estimated homicide rate,R = reported homicide rate, and N = number of reported homicides.

C Estimated undercount = (1-(R/E» 100.

12 Demography, Vol. 32, No.1, February 1995

year. Comparison with average upper and lower bounds of 95% confidence intervalssuggests an underreporting rate between 56.7% and 71.3%.

Unfortunately one cannot use the 1900-1906, Step 1 homicide estimates as x values inregression to further estimate national rates for those years. The equations would containerror terms that were correlated to an unknown degree, and would yield biased coefficients(Neter, Wasserman and Kutner 1985:164-67). Such a problem is difficult to overcome. It soturns out, however, that Step 1 violent death rates can be used directly to predict U.S.homicide rates, in the same way as they predicted homicide rates within the step and withsimilar robustness.

ESTIMATES OF NATIONAL HOMICIDE RATES

I estimate annual national homicide rates as described above. Because of the previouslydiscussed underreporting of homicide before 1907, for those years I estimate nationalhomicide rates using Step 1 rates for violent death rather than Step 1 homicide rates. Thisrelationship is strong, but it generates a wider confidence interval.

As an example, based on 1933-1950 data, the line describing the relationship betweenthe violent death rate in Step 1 (VIOLENCEsTEPl) and the U.S. homicide rate (HOMus) is

HOMus = -3.534 + (0.114 x VIOLENCEsTEPl)' (4)

In 1900 VIOLENCEsTEPI was 87.5, so the point estimate of HOMus is 6.4.Table 4 presents regression information showing relationships between homicide rates

in the nation and in the various steps. The weakest equation, employing as x values the rateof violent death in Step 1, accounts for 60% of variance in the national homicide rate. WhenStep 1 homicide rates are used, over 86% of the variance is explained. By Step 10 (1917),99% of the variance is explained. This finding implies a large general factor in U.S.homicide variation: fairly precise estimates of national rates can be made on the basis of datafrom a subset of states.

DISCUSSION

The estimates clearly do not support the previous historical picture of homicide in theUnited States. Although they do not reverse the findings of an early-century increase inhomicide, they indicate that the picture of rapid or progressive increases across the first thirdof the century is fundamentally false. Instead these estimates portray a moderate increaseduring the first five years of the century, six years of "random walk" stability, anotherincrease, then general stability again.

It may be, however, that all violent deaths were underreported in the early years. The1907 and 1908 reports (Mortality Statistics 1909:79-80; 1910:76-79) discuss strikingly highrates of death from "ill-defined and unknown causes" in the first years of the century-arate of 65.8 for the registration states in 1900, which declined by more than half by 1908.A portion of the initially high rate in this category represents a failure to include anyinformation about the cause of death, and it may include violent deaths.

If the 1900 and 1902 rates are accurate, then a relative increase of just under 50%occurs by 1914, with no significant increase thereafter. If one discounts those two years, theincrease is perhaps 25%. In any event, the relative increase between 1900 and 1914 (or even1933) seems to be no more than one-seventh as great as indicated by publishedregistration-area figures.

This discussion revises the picture of the century-long trend in U.S. homicide. Rather

20th Century U.S. Homicide Rates 13

Table 4. National Homicide Rate Estimates and Supportive Data, 1900-1932

Step 95% U.S.Year Step Rate Intercept Slope" RSQ RMSEb C.1. Estimate

1900 l c 87.55 -3.534 0.114 .600 0.514 +/-1.128 6.41901 98.99 1.147 7.71902 88.05 1.128 6.51903 98.62 1.145 7.71904 104.01 1.179 8.3

1905 102.67 1.169 8.11906 105.23 1.189 8.41907 l c 3.92 0.868 1.784 .868 0.325 0.734 7.91908 3.92 0.734 7.91909 3.46 0.716 7.1

1910 3.93 0.735 7.91911 6 5.55 0.336 1.505 .936 0.267 0.622 8.71912 5.38 0.614 8.41913 7 6.12 0.086 1.480 .956 0.221 0.527 9.11914 8 6.28 0.136 1.473 .956 0.213 0.517 9.4

1915 5.95 0.502 8.91916 9 6.42 -0.182 1.408 .971 0.161 0.379 8.91917 10 6.99 -0.210 1.328 .990 0.103 0.245 9.11918 6.10 0.231 7.91919 12 7.19 -0.148 1.156 .998 0.065 0.147 8.2

1920 6.84 0.145 7.81921 8.21 0.156 9.31922 14 8.03 -0.267 1.123 .999 0.055 0.128 8.71923 8.04 0.128 8.81924 8.37 0.131 9.1

1925 17 8.39 0.041 1.098 .999 0.038 0.089 9.31926 18 8.53 0.029 1.099 .999 0.036 0.087 9.41927 19 8.50 0.098 1.074 .999 0.028 0.067 9.21928 8.38 0.067 9.11929 8.07 0.065 8.8

1930 8.51 0.067 9.21931 8.89 0.069 9.71932 8.74 0.068 9.5

Sources: Mortality Statistics and Vital Statistics of the United States, various years; variouscensuses of the U.S. population.

a For all models, p<.OOI. In all cases I employ the available step whose equation yields thesmallest standard error of the estimate.

b Root mean square error (standard error of the estimate)c For years before 1907. I obtain parameters by regressing national rates across Step I rates of

violent death. Beginning with 1907. I obtain parameters by regressing national rates across step ratesof homicide. (See text for explanation.)

than seeing the lowest rates at the tum of the century, we find them in the 1950s. Even theestimates for 1900 and 1902 are more than 40% higher than are the rates in the mid-1950s.Aside from 1900 and 1902, the point estimate (or the actual rate, after 1932) is above 7.0

14 Demography, Vol. 32, No.1, February 1995

every year through 1937, or always substantially above the rates in the mid-1950s.Estimates for the period 1903-1912 generally are quite close to 8.0. From 1913 to the endof the period of incomplete registration (indeed, through 1934), estimates closely resemblethe rates since the early 1970s, remaining mostly above 9.0. The similarities are evident inFigure I.

The greatest caution is warranted for the earliest years in the century, but several factssupport the present estimates. These include the statements by the authors of MortalityStatistics, as well as the changes in absolute and relative rates of homicide and other violentdeaths, which point toward roughly a two-thirds underreporting of homicides early in thecentury. In addition, for many years the Step 1 states experienced rates of homicidedramatically lower than national rates (roughly half those rates). In combination, these factsimply that national rates in 1900-1904 were roughly 6 times the published rates for Step 1,close to what the estimates show.

Because of limitations in the quality of the data, most studies (including this one)employ crude rates. It is plausible that the changes we find are caused by changes in the agestructure of the population. Cohen and Land (1987) showed that such change has affectedhomicide rates in the United States since World War II, via changes in the proportion ofyoung males in the population. Gartner and Parker (1990) could not replicate this for theprewar years, and Vital Statistics-Special Reports (1956) found that age-adjusted rates for1900-1953 scarcely differed from crude rates. Both of these sources, however, usedregistration-area or registration-state rates as proxies for national rates.

I use time-series regression to test for effects of age structure on homicide rates in aconsistent unit: 1907-1940 data for Step 2 states (excluding South Dakota). Regressingannual homicide rates across the proportion of the step population youthful and male, I findno evidence of an age structure effect (p>.85, R2

= .0012). I also run regressions for eachfive-year age group of youthful males, using lags of one, two, and three years (resultsavailable on request). In no case is there a significant effect or an R2 of as much as 1%.

The present estimates do not allow one to make strong statements about a "civilizing"trend, because we lack comparable earlier data. Yet, although the United States has neverachieved rates of homicide as low as those in nations such as England, the general trend inthis century now appears similar. Apparently no enormous explosion of homicide occurredearly in the century. In fact, a moderating trend extended to the period after World War II.Finally, the increased rates in the past three decades are roughly double those of the 1950s,rather than five to nine times the rates early in the century, as previously appeared to be thecase.

We might hazard one tentative conclusion about long-term change in U.S. homicide. Ifthe long nineteenth-century decline described by several researchers (e.g., Gurr 1989) ledonly to rates consistent with the present first-decade estimates, we have no reason to believethat nineteenth-century national rates ever approached those of the mid-1950s. Rather, theymust be closer to (or even higher than) rates during the 1920s-1930s and the 1970s-1980s.because those rates are only moderately higher than were rates at the tum of the century.Conceivably, the peak homicide periods in the previous century were substantially moreviolent than is the present time.

This is certainly not to deny that homicide rates in the United States are dramaticallyhigher than in other industrialized countries (Fingerhut and Kleinman 1990). Thisdifference, however, is very old. Brearley (1932:27-28) discussed it over 60 years ago.Simply put, the U.S. homicide rate is relatively high and appears to have been so for asubstantial period-only one of several ways in which the United States has differed fromother industrialized countries. The present research indicates a way in which the U.S.experience may resemble that of such countries.

20th Century U.S. Homicide Rates

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