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Revista Brasileira de Epidemiologia

Print version ISSN 1415-790X

Rev. bras. epidemiol. vol.14 n.4 São Paulo Dec. 2011 



Fall in homicides in the City of São Paulo: an exploratory analysis of possible determinants



Maria Fernanda Tourinho PeresI, II; Juliana Feliciano de AlmeidaI; Diego VicentinI; Magdalena CerdaIII; Nancy CardiaI; Sérgio AdornoI, IV

ICenter for Violence Studies, Universidade de São Paulo
IIDepartment of Preventive Medicine, School of Medicine, Universidade de São Paulo
IIIDepartment of Epidemiology, Mailman School of Public Health, Columbia University. New York, USA
IVDepartment of Sociology, School of Philosophy, Languages and Literature, and Human Sciences, Universidade de São Paulo





Throughout the first decade of the 2000s the homicide mortality rate (HMR) showed a significant reduction in the state and the city of São Paulo (MSP). The aim of this study is to describe the trend of HMR, socio-demographic indicators, and the investment in social and public security, and to analyze the correlation between HMR and independent variables in the MSP between 1996 and 2008. An exploratory time series ecological study was conducted. The following variables were included: HMR per 100,000 inhabitants, socio-demographic indicators, and investments in social and public security. The moving-averages for all variables were calculated and trends were analyzed through Simple Linear Regression models. Annual percentage changes, the average annual change and periodic percentage changes were calculated for all variables, and the associations between annual percentage changes were tested by Spearman's correlation analysis. Correlations were found for the proportion of youth in the population (r = 0.69), unemployment rate (r = 0.60), State budget for education and culture (r = 0.87) and health and sanitation (r = 0.56), municipal (r = 0.68) and State (r = 0.53) budget for Public Security, firearms seized (r = 0.69) and the incarceration rate (r = 0.71). The results allow us to support the hypothesis that demographic changes, acceleration of the economy, in particular the fall in unemployment, investment in social policies and changes in public security policies act synergistically to reduce HMR in São Paulo. Complex models of analysis, incorporating the joint action of different potential explanatory variables, should be developed.

Keywords: Aggression. Homicides. Mortality. Ecological study. Time series studies. Brazil.




Throughout the first decade of the 21st century, the homicide mortality rate (HMR) significantly decreased in the state of São Paulo1,2. In the city of São Paulo, this rate dropped by 74% between 2001 and 2008, from 56.4 to 14.9 per 100,000 inhabitants3. According to Peres and cols. (2011)3, this reduction was widespread, reaching both urban areas and different population groups, with a trend towards approximation and reduction in inequalities in the risk of death.

The role of public security measures in the reduction in HMR has been widely discussed in studies conducted in the United States, especially in New York4,5,6,7,8. The international literature also emphasizes the importance of demographic, socioeconomic and drug use pattern changes to reduce violence and crime levels4,8,9,10.

In studies conducted in the state or metropolitan area of São Paulo, the increase in incarceration and disarmament rates and decrease in the proportion of adolescents in the population were tested and found to be associated with the reduction in HMR by Nadanovisky (2009)2, Cerqueira & Mello (2010)ª and Mello and Schneider (2007)11, respectively. In addition to the factors mentioned above, authors have discussed other yet untested hypotheses: an improvement in socioeconomic development indicators, preventive actions implemented by the municipal government, and greater social participation through organized civil society actions are among the factors considered to be important1,3,11,12. A possible role of stronger organized crime, which would function as a new social control mechanism that mediates local conflicts, has been pointed out in ethnographic studies as the factor responsible for the reduction in crime in São Paulo3,12,13,14,15.

There are few, if any, studies that have analyzed the relationship between HMR and investment in social policies. It could be assumed that greater investment in social actions, especially in areas where there are more disadvantages, could reduce the possibility of conflicts as a result of a greater positive presence of the State as a reference and mediating institution16. According to Kawachi and cols. (1997)17, investments in social policies reflect and contribute to greater social capital, which, in its turn, is associated with lower violence levels. In this way, it could be assumed that the increase in social actions, policies and programs has a positive impact on the reduction in violence levels, a hypothesis that has yet to be proved.

The present study aimed to describe the trend of the HMR, socio-demographic indicators and investments in social policies and public security, and to analyze the correlation between the trend of the HMR and the independent variables in the city of São Paulo, between 1996 and 2008. This study had an exploratory design and its results will contribute to the refinement of explanatory hypotheses about the sharp reduction in mortality from homicide observed in São Paulo in recent years.



An exploratory, ecological time-series study was conducted and the unit of analysis was the city of São Paulo, between 1996 and 2008.

Data on death by homicide of residents occurred in this city were collected from the database of the Programa de Aprimoramento das Informações sobre Mortalidade da Prefeitura do Município de São Paulo (PROAIM - City of São Paulo Mortality Information Improvement Program)b. The PROAIM uses the Death Certificate (DC) as the primary source of data and all causes of death are coded according to the International Classification of Diseases - 10th revision (ICD-10). Cases coded as death by Assault (X85 to Y09) and Legal Intervention (Y35 to Y36) were considered as death by homicide. Population data from the IBGE (Brazilian Institute of Geography and Statistics) and projections made by the Fundação SEADE (State Data Analysis System Foundation) for the inter-census years were obtained from São Paulo City Hall websitec. HMRs per 100,000 inhabitants were standardized per age according to the direct method, using the population of the city of São Paulo in 2000 as the standard population.

Population data from the IBGE and projections of the Fundação SEADE were used to calculate the proportions of adolescents in the population of the city of São Paulo3. The rate of unemployment in this city was obtained from the Secretaria Municipal de Planejamento Urbano (Sempla - City of São Paulo Department of Urban Planning) website for 1991 and the period between 2000 and 2007d. Time-series gaps were filled with projections made in STATA 10.0, using the linear interpolation and extrapolation method with the ipolate y x, gen(newvar) epolate command. Time-series gaps were filled using this command, assuming there is a linear relationship between the variable of interest (unemployment) and, in this case, the "year" variable. According to Sempla, the unemployment rate takes into consideration open unemployment - which includes all individuals who sought a job during a period of 30 days and did not perform any work - and hidden unemployment - which includes those who performed precarious and unpaid work and who are not working, although they sought a job in the previous 12 months.

Data on state and municipal spending on education and culture, health and sanitation, and public security were obtained from the Department of National Treasury website for the period between 1997 and 2008e.

The proportion of state and municipal budgets was calculated according to the total state and municipal spending, and the total spending of each department (education and culture, health and sanitation and public security) per unit (State and City) per year. The values found in 1997 were repeated in 1996 to complete the time series.

Data on the number of firearms seized by the police in the city of São Paulo were collected from the Secretaria de Segurança Pública (SSP/SP - State of São Paulo Department of Public Security) websitef. The number of firearms seized per 100,000 inhabitants was calculated, according to the IBGE population census data and Fundação SEADE projections for the city of São Paulo. The number of arrests made while in the act or with a warrant in the city of São Paulo was obtained from the SSP/SP website6 as an indicator of police activity in this city; the respective rate per 100,000 inhabitants was calculated from population data on the city of São Paulo.

In the context of the penitentiary system, all prisoners (temporary or sentenced) found in temporary detention centers and police stations were considered in the calculation of the arrest-incarceration rate. Such information was available on the Department of Penitentiary Administration websiteg. The population aged 18 years or more living in the state of São Paulo was considered in this study, including the arrest-incarceration rate per 100,000 inhabitants aged 18 years or more.

Data were processed using Microsoft Excel. Annual percentage variations, annual mean variations and periodical percentage variations of all variables were calculated for the three periods: global (1996 to 2008), initial (1996 to 2001) and final (2001 to 2008). Data were transferred to STATA 10.0 to describe the distribution and to analyze the existence of a possible association between the HMR trend and the independent variables. Moving averages of all study variables were calculated to analyze the trend. Simple linear regression models were constructed with each of the variables, using the year variable as independent variable. Line graphs were also constructed with the moving averages to make a visual analysis of trend curves. Spearman's correlation analysis was performed among annual percentage variations of variables to make an exploratory investigation of the association.

The present study was approved by the Comissão de Ética para Análise de Projetos de Pesquisa (CAPPesq - Research Project Analysis Ethics Committee) of the HCFMUSP (Universidade de São Paulo School of Medicine Clinical Hospital) (Protocol number 1358/09). Authors declared there were no conflicts of interest.



The HMR decreased 68.8%, from 47.6 in 1996 to 14.9 per 100,000 inhabitants in 2008 (Table 1; Graph 1). The curve tends to decrease, as shown in Table 2, with a mean reduction in HMR of 3.08 per year and coefficient of determination (R2) of 84.4% (Table 2). Graph 1 shows that the fall begins in 2001 and becomes sharper in 2003. In the final period of the series, the percentage reduction was -73.7% and the mean annual reduction was -17% (Table 1).