摘要：Objectives. We assessed whether New York City's gun-related homicide rates in the 1990s were associated with a range of social determinants of homicide rates. Methods. We used cross-sectional time-series data for 74 New York City police precincts from 1990 through 1999, and we estimated Bayesian hierarchical models with a spatial error term. Homicide rates were estimated separately for victims aged 15–24 years (youths), 25–34 years (young adults), and 35 years or older (adults). Results. Decreased cocaine consumption was associated with declining homicide rates in youths (posterior median [PM] = 0.25; 95% Bayesian confidence interval [BCI] = 0.07, 0.45) and adults (PM = 0.07; 95% BCI = 0.02, 0.12), and declining alcohol consumption was associated with fewer homicides in young adults (PM = 0.14; 95% BCI = 0.02, 0.25). Receipt of public assistance was associated with fewer homicides for young adults (PM = –104.20; 95% BCI = –182.0, –26.14) and adults (PM = –28.76; 95% BCI = –52.65, –5.01). Misdemeanor policing was associated with fewer homicides in adults (PM = –0.01; 95% BCI = –0.02, –0.001). Conclusions. Substance use prevention policies and expansion of the social safety net may be able to cause major reductions in homicide among age groups that drive city homicide trends. Most large US cities experienced a decline in homicide during the 1990s. However, nowhere was the decline more publicized than in New York City. 1 – 4 The city's homicide drop in the 1990s was the largest in its postwar history 1 : homicides declined from 2245 in 1990 to 633 in 1998—a drop of 72% over 8 years. 2 Two leading theoretical perspectives have guided interpretations of the mechanisms behind New York City's decline in homicide. One of the most prominent theoretical perspectives is the theory of “broken windows” policing, 5 which proposes that failure to control minor offenses creates a sense of public disorder and encourages the proliferation of crime. This theory motivated investment in increased policing of misdemeanors during the 1990s. Research studying this approach's impact on homicide have produced conflicting evidence; studies exist that report no evidence of reduced homicide associated with misdemeanor policing, 6 , 7 modest reductions in homicide, 3 , 4 , 8 and significant reductions in crime. 9 , 10 The second theoretical framework, the “crack cocaine” thesis, attributed the increase in homicide in the 1980s to the appearance of crack cocaine in the drug markets of large cities. 11 – 13 This phenomenon was accompanied by heavy recruitment of young male dealers, creating an increased need for use of guns. Blumstein proposed that the drop in homicide in the 1990s was caused by shifting drug markets, police response to gun carrying by young men, efforts to decrease general access to guns, an increase in the prison population, and economic expansion. 11 , 12 Previous studies of the determinants of the New York City homicide decline have built on these theoretical perspectives and used pooled cross-sectional time-series designs, as well as natural experiments, to investigate the impact on overall homicide rates of the following phenomena: improvement in policing of low-level, quality-of-life offenses 3 , 4 , 9 , 10 , 14 , 15 ; a decline in drug-market activity, with fewer turf wars between drug-dealing crews 11 , 12 , 16 – 18 ; reduced firearm availability as a result of federal and city-level efforts to limit access to and licensing of handguns and assault weapons 16 , 19 , 20 ; the removal of dangerous persons from the streets via implementation of proincarceration policies 15 , 16 , 21 , 22 ; and a decline in alcohol consumption after the instatement of a consumption tax on beer and hard liquor. 2 Previous time-series analyses 3 , 4 , 8 have examined the influence of these social determinants on overall homicide, and the current study expands upon that literature by separately examining how such factors are related to homicide victimization in specific age groups. The risk of homicide varies sharply by age, 23 – 25 and homicide rates in different age groups may result from different sets of risk factors. Indeed, the differential response to social changes by age group may have contributed to the significant shift in the age structure of homicide in the United States in the 20th century. 15 , 26 , 27 In New York City, the dramatic drop in homicides in the 1990s benefited some age groups more than others 2 , 28 : adolescents aged between 16 and 19 years and young adults aged 20 to 29 years experienced the sharpest decreases in homicide of all age groups. Focusing on age-specific rates rather than on overall population rates may allow us to understand the drivers of the homicide rates for the age groups that are causing the overall rates to rise and fall. Therefore, in this analysis, we replicated the pooled, cross-sectional time-series design used in previous studies of the overall homicide rate to compare how social determinants of changes in total homicide levels in New York City (i.e., misdemeanor policing, cocaine consumption, firearm availability, incarceration rates, and alcohol consumption) influenced age-specific gun-related homicide rates in the 1990s.
