1. PREDICTING THE 2013 SAINT LOUIS CITY HOMICIDE RATE SPENCER SCHNEIDENBACH SHAILESH LANJEWAR XUN ZHOU BEN HOLTMAN

2. BACKGROUND Annual homicide rates for 157 large US cities Analyzed for 30 years – 1976 to 2005 Factors Resource deprivation/concentrated poverty Higher income inequality Higher percentage of divorced adult male population Higher unemployment rates Study in 30 nations Significant association between poverty and homicide Sources: http://www.sciencedirect.com/science/article/pii/S0049089X10001882 http://www.sciencedirect.com/science/article/pii/S0049089X10001882 http://www.sciencedirect.com/science/article/pii/S0049089X12002554

3. DIVERSITY Characteristics of neighborhoods Very significant in predicting homicide Conclusion: immigrant concentration unrelated or inversely related to homicide language diversity consistently linked to lower homicide 15 years of data (1980-1994) St. Louis Homicide rate related to neighborhood characteristics Patterns differ according to homicide subtypes – general altercation, felony and domestic Sources: http://hsx.sagepub.com/content/13/3/242.shorthttp://hsx.sagepub.com/content/13/3/242.short http://onlinelibrary.wiley.com/doi/10.1111/j.1533-8525.2003.tb00536.x/abstract

4. NATIONAL GANG TRENDS Source: FBI 2011 National Gang Threat Assessment – Emerging Trends

5. MISSOURI GANG TRENDS Source: FBI 2011 National Gang Threat Assessment – Emerging Trends

6. MISSOURI GANG TRENDS  Seems to be lower than other states with only 0-2 members per 1000 people  Rise in gang “promotional teams”  Increased gang use of social media directed towards youth  Presence small as it may be of 490 gangs according to the FBI Gang Threat Assessment Source: FBI 2011 National Gang Threat Assessment – Emerging Trends

8. DATA SELECTION PRINCIPLE Timeliness - Annually? Quarterly? Monthly? Sufficiency - Sample size – St Louis City, at least 5 years, the factors can have potential impact on criminal Level of detail or aggregation - Amount for reported criminal annually, criminal ratio distribute by district and possible influence factors such as poverty level, education attainment, population, Income etc Understandability - Readable for the crime data. Freedom from bias - How to avoid that? Keep it simple Decision relevance - How to determine the boundary? Geographical? How many factors are relevant to the criminal occurs geographically?

9. DATA SELECTION PRINCIPLE Comparability - Each city is individual case for analytic, avoid comparing the other cites’ data and cut off the data which influenced by abnormal factors. Reliability - We can not control, however there may be un-reported and un- detected crime which can influence the analysis Redundancy - Mulit-resources? Cost efficiency - Costs concern update data annually Quantifiability - Use Ratio level data Appropriateness of format - Which is the appropriate way to demonstrate

10. DIMENSIONALITY OF MODELS Representation -Reported crime Time Dimension -How much of the activity of decision environment is being considered Linearity of the Relationship -Determine if categorized data are linear or nonlinear Deterministic Versus Stochastic -Linear regression, Stochastic modeling Descriptive Versus Normative - Descriptive - used for prediction

11. DIMENSIONALITY OF MODELS Causality versus correlation -How to determine? - use criminal distribution graph and the other possible factor which has the positive or negative relate on them Methodology Dimension -Complete enumeration, algorithmic, heuristic simulations and analytical -Complete enumeration – large sample amounts required -Algorithmic – extremeness' value method -Heuristic - if math would not help -Simulation – external influence? Hard to identify -Analytical – speared parts for the whole process

12. MODELS WE CONSIDERED  Linear regression  Model based on Census, American Community Survey data  Predict crime based on population factors -Saint Louis Police Department Neighborhood Statistics -U.S. Census American Fact Finder Statistics -American Community Survey -Poverty Level -Educational Attainment -Lack of Core Family Stability Single Parent Families – Mothers with no husband present -Income -Race

13. MODELS WE CONSIDERED (CONT)  Linear Regression  Census data  Research only occurs once a decade  Hard to measure trends for predictions  American Community Survey  Broken down at the macro level (entire city)  Can’t measure by neighborhood, district  Conclusion:  Still useful for identifying problem areas inside a city  Best for a one-time “snapshot” to see what correlations exist and attack those problems  Largely outside the scope of what the SLMPD does

14. MODELS WE CONSIDERED (CONT)  Rolling average  Model based on past homicides  Weighs more recent data higher than other data  Pros  Data is easily accessible and accurate  Model is simple and pretty accurate  Cons  Does not predict big, one time events  Model data varies the more homicides are committed

15. MODELS WE CONSIDERED (CONT)  Rolling average  District vs. neighborhood  SLMPD uses districts  Most crime seems to be concentrated in several large areas  Districts it is  Quarters, months, years?  Years – too macro  Months – too micro – data is too wildly distributed  Measuring by quarters provides a nice balance between micro vs. macro and data accuracy

16. DECISION POINT  Rolling average it is  Regression model can’t be trended  Best model based on all available data

17. EXAMPLE MODEL  Rolling average it is  Best model based on all available data  Our model:  Prediction based on last 4 quarters  Last quarter: weighted by 0.4  2 nd last: 0.4  3 rd last: 0.1  4 th last: 0.1

18. MEASURING THE MODEL

19. OUR PREDICTIONS

20. CONCLUSION  Prediction is difficult

21. QUESTIONS?

22. SOURCES FBI 2011 National Gang Threat Assessment – Emerging Trends. http://www.fbi.gov/stats- services/publications/2011-national-gang-threat-assessmenthttp://www.fbi.gov/stats- services/publications/2011-national-gang-threat-assessment Saint Louis Police Department Statistics - http://www.slmpd.org/Crimereports.shtmlhttp://www.slmpd.org/Crimereports.shtml American Fact Finder - http://factfinder2.census.gov/faces/nav/jsf/pages/guided_search.xhtmlhttp://factfinder2.census.gov/faces/nav/jsf/pages/guided_search.xhtml Saint Louis Homicide Map - http://blogs.riverfronttimes.com/dailyrft/2013/01/st_louis_city_homicide_map_nextstl.php