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5 An Empirical Assessment of the Contemporary Crime Trends Puzzle: A Modest Step Toward a More Comprehensive Research Agenda--Eric P. Baumer
5 An Empirical Assessment of the Contemporary Crime Trends Puzzle: A Modest Step Toward a More Comprehensive Research Agenda--Eric P. Baumer
Pages 127-176
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From page 127... ...
I begin with an overview of the state of the existing research and then outline the ways in which the present study goes beyond previous efforts. I then describe the sample and data used in the empirical analysis, summarize the key empirical findings and assess them in comparison to conclusions drawn in other recent studies, and close with a call for additional research that can build on the analysis to help establish the kind of research agenda needed to make significant progress in developing a more definitive portrait of the determinants of recent crime trends.
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From page 128... ...
However, the existing empirical research on recent crime trends is in the early stages of development and is not at the point of sufficient breadth or depth to provide definitive evidence on which factors mattered a lot, which mattered relatively little, and, importantly, which mattered the most. The research community appears to have been reluctant to admit this apparent fact, concluding instead that the available evidence supports either the conclusion that virtually all of the dozen or so factors implicated in the theoretical literature played some role in shaping recent crime trends or the conclusion that one or more specific factors were very important and others mattered little.
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From page 129... ...
But if the hypothesized causes have been identified, why Illicit Drug Use Alcohol Police Force and Market Consumption Firearm Size Activity Prevalence Public Order and + + + Weapons Enforcement _ _ Incarceration _ Volume of + Crime Offender Reentry Rates + _ Unemployment _ _ Wages for + Legal Work Percent Age Immigration Percent Age 45 and Older 15 to 24 Levels _ _ High-Risk Births Levels of and Births to High-Risk Fertility Control, t-15-24 Women, t-15-24 FIGURE 5-1 Heuristic model of hypothesized main effects on recent crime trends. Figure 5-1, fully editable
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From page 130... ...
are rarely considered simultaneously. There are several excellent empirical papers on recent crime trends that provide persuasive evidence that a given factor was critical to shaping recent trends, yet most of the factors identified in Figure 5-1 have not been evaluated empirically very often or in systematic ways and, even when they are examined, the overall body of relevant empirical research on crime trends suffers from two major limitations that have served as impediments to establishing a more definitive body of knowledge on why crime rates have taken their observed path since the early 1980s: (1)
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From page 131... ...
, they have not considered age- or crime-specific incarceration rates, average sentence length, time served, or prisoner release rates, even though these factors have been highlighted as potentially important in theoretical discussions and are available as data elements in the public domain. It is also noteworthy that none of the existing studies of recent crime trends has included indicators of recent immigration flows and, surprisingly, only a few have incorporated direct indicators of changes in the nature of policing across multiple geographic units (MacDonald, 2002; Messner et al., 2007; Rosenfeld, Fornango, and Rengifo, 2007)
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From page 132... ...
With respect to the former issue, research on recent crime trends has been conducted across multiple units of analysis, most often states, counties, cities, neighborhoods, and police precincts. It is not necessarily important that a particular unit of analysis be identified, a priori, as superior for studying crime trends, for the reality is that each of these units has conceptual merit, and there are important trade-offs in the choice of unit.
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From page 133... ...
. The main contribution, then, lies in an expansion of the empirical specification typically applied in research on recent crime trends -- it is the first study of which I am aware that examines simultaneously each of the major factors shown in Figure 5-1 that have been emphasized in theoretical and policy discussions of recent crime trends.
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From page 134... ...
These matters are not merely statistical exercises; they have important implications for the inferences drawn about crime trends. Although there is important work being done on these issues both in criminology and other disciplines, collectively they represent a challenging set of issues that is more complex than often portrayed in the literature and which cannot be addressed satisfactorily here given the space constraints of this volume. Instead, although the present work expands on recent crime trends research by considering a much larger set of the factors most commonly emphasized in theoretical discussions, it applies the same econometric tools used in many existing subnational studies.
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From page 135... ...
But I elaborate on some relatively neglected issues and outline the ways in which I go beyond past work. Reconsidering Commonly Addressed Factors Two factors that have received a particularly high level of attention in public discourse on recent crime trends, and especially the 1990s crime decline, are changes in policing and incarceration.
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From page 136... ...
The present study therefore estimates models of crime for both stock and flow measures of incarceration to evaluate in a more comprehensive manner the role of incarceration in shaping recent crime trends. Considering the prison flow measures not only provides a more precise look at incarceration effects than relying solely on the stock incarceration rate, but it also permits an independent assessment of prison releases on recent crime trends.
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From page 137... ...
The role of illicit drug use and market activity, especially with respect to crack cocaine, also has received a good deal of attention in the theoretical and empirical literature on recent crime trends. Although there are some doubters (e.g., Zimring, 2006)
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From page 138... ...
Some of the evidence in support of the hypothesized connection can be criticized for being generated from empirical models that omit many of the other factors thought to be relevant to recent crime trends. Also, although some scholars have emphasized the possible interactive effects of drug markets and the legitimate economy on recent crime trends, aside from assessments of the contingent role of drug markets in areas with different levels of economic and social disadvantage (e.g., Ousey and Lee, 2004)
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From page 139... ...
Attending to Some Neglected Factors In addition to evaluating some expanded measures of commonly considered causes of recent crime shifts, I also examine several factors highlighted in theoretical and policy discussions but rarely examined systematically in the empirical literature. These include changes in alcohol consumption, legal wages, levels of domesticity, immigration, and birth cohort quality.
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From page 140... ...
Although a variety of demographic features have been alluded to in the literature as potentially relevant to recent crime trends, the existing empirical literature has taken a relatively narrow approach to measuring the role of demography. This work adds to the literature by explicitly considering three demographic factors highlighted in theoretical and policy discussions of recent crime trends but that have received meager attention in the empirical literature: levels of domesticity (Rosenfeld, 2006)
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From page 141... ...
Another demographic feature that has been linked to recent crime trends in the United States is the level of immigration. In a 2006 New York Times op-ed contribution, Sampson extrapolated from the findings revealed in recent individual- and multilevel studies of the role of immigrant status in shaping involvement in crime and violence (e.g., Butcher and Piehl, 1998; Sampson, Morenoff, and Raudenbush, 2005; for reviews, see Hagan and Palloni, 1998; Martinez and Lee, 2000)
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From page 142... ...
. Yet there is relatively little systematic empirical evidence on the link between immigration and crime at the aggregate level, and only three s tudies of which I am aware consider empirically the role of immigration on recent crime trends (Butcher and Piehl, 1998; Rosenfeld, Fornango, and Rengifo, 2007; Sykes, Hangartner, and Hathaway, 2007)
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From page 143... ...
Much of the research attention on and discussion about the abortion dividend argument understandably has focused exclusively on the direct link between 1970s abortion law changes and recent crime trends. Although some observers have expressed skepticism about this link because the timing of abortion law changes and the beginning of observed declines in the 1990s do not coincide neatly (e.g., Blumstein and Wallman, 2006a; Fox, 2006; Rosenfeld, 2004)
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From page 144... ...
to link abortion to contemporary crime trends. In my view, the key criminological and more proximate causal questions that emerge from their work are not whether abortion laws are associated with crime trends, but rather whether recent crime trends were significantly shaped by (1)
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From page 145... ...
One of the significant omissions from the existing empirical literature is a simultaneous assessment of the many factors hypothesized to shape recent crime trends. The attempt here is to fill this gap by considering the effects on crime trends of each of the major factors emphasized in the literature and discussed above.
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From page 146... ...
About one-third of the sample attrition arose because of the inclusion of disaggregated homicide rates in the study, which were available on a consistent basis across the study period for only 205 of the 240 original cities. Much of the remaining attrition was due to the inclusion of key explanatory variables, especially indicators of drug market activity and drug use, which contain a substantial amount of missing data.
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From page 147... ...
Second, because the census data on social and economic attributes included in the NRC database were available for only 3 of the 25 time points examined in the study, I drew from a variety of additional sources to construct annual indicators of these conditions. Finally, some of the conditions emphasized in the literature as potentially important for understanding recent crime trends, such as the prevalence of firearms, levels of immigration, domesticity, alcohol consumption, birth cohort conditions, and wages received for legal work were not included in the NRC data, so I added measures of them to the data.
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From page 148... ...
4,144.75 1,951.18 1,410.78 Motor vehicle theft rate Motor vehicle thefts per 100,000 motor vehicles (UCR and 807.70 1,056.05 471.88 Census Bureau) Explanatory Variables Criminal justice factors State stock incarceration ratet-1 Persons incarcerated in state prison per 100,0000 residents (BJS)
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From page 149... ...
woment-15-19 years MSA % of births < 2500 % of babies born in MSA who weighed < 2,500 grams, lagged 7.34 1.09 .496 gramst-15-19 years 15-19 years (NCHS Natality Files) NOTE: BEA = Bureau of Economic Analysis; BJS = Bureau of Justice Statistics; BLS = Bureau of ���������������������������������������������������� Labor Statistics; FARS = Federal Accident Reporting System; INS = Immigration and Naturalization Service; MSA = metropolitan statistical areas; N��������������������������������������������������� ������������������������������������������������������������������������������������������ CHS = National Center for Health Statistics; NHTSA = National Highway and Traffic Safety Administration; SEER = Surveillance Epidemiology and End Results; SHR = Supplementary Homicide Reports; � ��������������������������������������� 149 UCR = Uniform Crime Reporting Program.
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From page 150... ...
. The typical subnational study of recent crime trends assumes stationarity in the variables and proceeds by estimating panel regression models in levels (for some exceptions, see McDowall, Loftin, and Wiersema, 2000; Moody and Marvell, 2005)
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From page 151... ...
None of the available strategies is ideal or fully satisfactory under typical conditions, but addressing this issue is critical for drawing more definitive conclusions about the factors associated with recent crime trends. Granger tests are useful for assessing whether simultaneous relationships are present, but it appears that the greatest strides in tackling the endogeneity problem in crime trends research will come in the form of identifying and incorporating valid and relevant instrumental variables that can help separate simultaneous effects (see also Spelman, 2008)
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From page 152... ...
Although this is a common strategy, extensions of this research should assess its validity by incorporating instrumental variables as noted above. In summary, the analysis presented below adopts methods that have been used in most of the extant research on recent crime trends, yet it extends that work by incorporating, to a much greater degree, indicators of each of the major factors emphasized in theoretical and policy discussions.
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From page 153... ...
Finally, the implications of the results for predicting subsequent crime rates are outlined. A Comprehensive Model of Recent Crime Trends Table 5-2 displays estimates for two-way fixed-effects panel regression models for the 114 cities included in the analysis for the full study period (1980-2004)
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From page 154... ...
(.029) City police force sizet–1 (logged)
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From page 155... ...
(.145) City police force sizet–1 (logged)
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From page 156... ...
(.039) City police force sizet–1 (logged)
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From page 157... ...
(.187) City police force sizet–1 (logged)
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From page 158... ...
The estimated coefficients were not consistently significant across crime types, but the pair of coefficients for these two indicators of prison flow (i.e., admissions and releases) is statistically significant at conventional levels for four of the eight crime types considered (overall homicide, gun homicide, robbery, and burglary)
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From page 159... ...
There is no evidence in the data that cities in which the police focused more heavily on public order and weapons offenses (as measured by arrest rates) exhibited significantly lower crime rates.
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From page 160... ...
Fourth, the evidence for the effects of guns, drug activity, and alcohol consumption on recent crime trends is mixed. Trends in alcohol consumption do not appear to play a significant role in shaping recent crime trends, firearm prevalence is significantly associated with overall homicide but not other crimes, and the indicators of change in crack cocaine use and market activity exert significant and meaningful effects on recent crime trends, albeit in somewhat inconsistent ways across measures and crime types.
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From page 161... ...
and with a measure of city-level rates of immigration (i.e., the number of immigrants intending to live in the sampled cities -- not merely the metropolitan statistical areas in which they are located -- per 100,000 city residents) does not yield such a pattern and, more importantly, affirms that the most consistent pattern is that immigration flows are not significantly associated with recent crime trends.
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From page 162... ...
The Relative Contribution of the Factors Overall, what do these findings tell us about which factors contributed most to contemporary crime trends? As noted above, a much more rigorous analysis should be applied to the data before one can draw precise conclusions about the bigger picture, but to address this issue in a preliminary way and make general comparisons with recent overviews of the research, I used the results shown in Table 5-3, coupled with information about observed changes in crime rates and the explanatory variables, to compute the estimated percentage of the overall change in crime rates that can be attributed to each factor considered.
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From page 163... ...
. Although the role of the three indicators of drug market activity and drug use vary across crime types, the results suggest that together they account for between 20 and 40 percent of the observed increases in overall homicide, gun homicide, and youth homicide and about 10 percent of the observed increase in robbery rates.
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From page 164... ...
I have argued in this chapter that taking a more comprehensive approach to measuring and modeling the factors thought to be associated with recent crime trends could yield different conclusions. In fact, this does appear to be the case.
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From page 165... ...
The results in Table 5-3 yield very similar estimates, indicating that about 3-7 percent of the observed decline in crime during the 1990s can be attributed directly to increased police forces, with property crimes defining the lower end and adult homicide and nongun homicide defining the upper end. The other factors examined do not appear to have played a major role in the 1990s crime decline, at least as I have measured and modeled them.
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From page 166... ...
, levels of domesticity, immigration rates, alcohol consumption, and firearm prevalence may emerge as more relevant in analyses that better attend to issues of measurement error, unit measure mismatch, stationarity, and simultaneity, but for now I would conclude that their contributions to the 1990s crime decline do not appear to be substantial. Out-of-Sample Predictions Thus far I have focused on attempting to explain what happened with respect to recent crime trends.
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From page 167... ...
In each of these three cases, for instance, one would have predicted decreases TABLE 5-5 Predictions of 2005 Crime Levels for 50 Largest Cities from Regressions of Recent Crime Trends, 1980-2004 Homicide Robbery Burglary Auto Theft % Change 2004-2005 Predicted –2.74 –.40 –.39 –.27 Observed 3.79 1.02 .01 –.34 % Cities predicted in right direction 44 40 46 48 NOTE: Figures for predicted and observed change represent median values for the 50 largest cities in the sample for which this information could be computed.
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From page 168... ...
With respect to the latter, as noted earlier, one of the more important factors in explaining recent crime trends -- incarceration -- appeared in this study to exhibit some nonlinear and temporally variable effects, and these were not captured in the prediction exercise summarized above (the pooled estimates were used instead)
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From page 169... ...
Most of the extant literature has focused on a small number of potentially relevant factors, even though the theoretical literature highlights numerous other f actors that may have been important for shaping recent crime trends. Taking a more comprehensive measurement approach required, in some cases, the use of state-, metropolitan area-, and county-level explanatory variables to explain city-level crime rates (cities were the unit of analysis chosen by the NRC)
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From page 170... ...
are nonstationary, the results that emerge could be spurious, which obviously has important implications about the most important factors in shaping recent crime trends. A variety of methodological issues need to be sorted out to satisfactorily address the time-series properties of variables considered, many of which currently are or have been explored (Baumer and Rapach, 2007; Moody, 2007; Spelman, 2008)
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From page 171... ...
. Why crime rates fell.
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From page 172... ...
. The emergence of crack cocaine and the rise in urban crime rates.
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From page 173... ...
. The effect of prison population size on crime rates: Evidence from prison overcrowding litigation.
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From page 174... ...
. The impact of youth curfew laws on juvenile crime rates.
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From page 175... ...
. The contribution of ex-prisoners to crime rates.
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From page 176... ...
. The great American crime decline.
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