1. Rotational grid, PAI maximizing
Crime Forecasts
George Mohler
Indiana University –
Purdue University Indianapolis
PredPol
Mike Porter
University of Virginia
PASDA
BRIEFLY INTRODUCE YOURSELF AND YOUR INVESTIGATORS (10 sec slide)

2. NIJ Solution CrimeRank Policing Fairness Social Harm
Crime Models Should Address
long-term intrinsic risk
short-term dynamic risk
time of day/day of week trends (not applicable for NIJ Challenge)

3. NIJ Solution CrimeRank Policing Fairness Social Harm
Crime Models Should Address
long-term intrinsic risk
short-term dynamic risk
time of day/day of week trends (not applicable for NIJ Challenge)
geometry of city
evaluation metric (PAI or PEI)

4. NIJ Solution CrimeRank Policing Fairness Social Harm
Our approach
parameterize grid
cell features
point processes
counts
supervised learning
random forest
sparse regression
simplex method to maximize PAI
Mohler and Porter, Rotational Grid PAI Maximizing Crime Forecasts, Statistical Analysis and Data mining, 2018.

5. NIJ Solution CrimeRank Policing Fairness Social Harm
Our approach
parameterize grid
cell features
point processes
counts
supervised learning
random forest
sparse regression
simplex method to maximize PAI
Mohler and Porter, Rotational Grid PAI Maximizing Crime Forecasts, Statistical Analysis and Data mining, 2018.

6. NIJ Solution CrimeRank Policing Fairness Social Harm
Our approach
parameterize grid
cell features
point processes
counts
supervised learning
random forest
sparse regression
simplex method to maximize PAI
PAI COMPETITION TABLE
Mohler and Porter, Rotational Grid PAI Maximizing Crime Forecasts, Statistical Analysis and Data mining, 2018.

7. NIJ Solution CrimeRank Policing Fairness Social Harm
Mohler & Porter et al, Learning to Rank Spatio-Temporal Event Hotspots,
UrbComp 2018.

8. NIJ Solution CrimeRank Policing Fairness Social Harm
Model the “gradient” of PAI
Fit a regression tree to the gradient
Update score Si with one step of gradient ascent
Mohler & Porter et al, Learning to Rank Spatio-Temporal Event Hotspots,
UrbComp 2018.

9. NIJ Solution CrimeRank Policing Fairness Social Harm
Mohler, G. O., Short, M. B., Malinowski, S., Johnson, M., Tita, G. E., Bertozzi, A. L., & Brantingham, P. J. (2015). Randomized controlled field trials of predictive policing. Journal of the American Statistical Association, 110(512),
7% reduction in crime, 30 min patrol a day
Ratcliffe, Jerry H., et al. "The Philadelphia foot patrol experiment: A randomized controlled trial of police patrol effectiveness in violent crime hotspots." Criminology 49.3 (2011):
23% reduction in crime, 16 hours of foot patrol a day
Saunders, Jessica, Priscillia Hunt, and John S. Hollywood. "Predictions put into practice: a quasi-experimental evaluation of Chicago’s predictive policing pilot." Journal of Experimental Criminology 12.3 (2016):
no difference between treatment and control

10. NIJ Solution CrimeRank Policing Fairness Social Harm

11. NIJ Solution CrimeRank Policing Fairness Social Harm
Lum, Kristian, and William Isaac. "To predict and serve?." Significance 2016.
Brantingham, P. Jeffrey, Matthew Valasik, and George O. Mohler. "Does Predictive Policing Lead to Biased Arrests? Results From a Randomized Controlled Trial." Statistics and Public Policy  2018.
G. Mohler, M. Porter, R. Raje, J. Carter,  M Valasik, and PJ Brantingham.  A penalized likelihood method for balancing accuracy and fairness in predictive policing.  SMC2018.
biased feedback loops possible: drug crime
bias not detected in property crime field trial
demographic parity through MPLE, at cost to PAI

12. NIJ Solution CrimeRank Policing Fairness Social Harm
Ratcliffe (2015) “Towards an Index for Harm-focused Policing” Policing 2015.
Sherman et al (2016) “The Cambridge Crime Harm Index: Measuring Total Harm from Crime Based on Sentencing Guidelines” Policing 2016.
Mohler, Carter, and Raje (2018) “Improving social harm indices with a modulated Hawkes process” International Journal of Forecasting 2018.
Why not take a cost-benefit analysis point of view. There wasn’t anything necessarily special about burglary and vehicle crime in our trial. Several criminologists have proposed social harm indices to be more systematic in the approach to policing. Here the cost of crime is quantified, which could be monetary, prison sentence length, or an integer score.
Indianapolis: 12.5% of $1billion/yr captured in 1% of city

13. Acknowledgements
National Institute of Justice
National Science Foundation
Smart and Connected Communities
Algorithms for Threat Detection
Andrea Bertozzi (UCLA Math)
Jeff Brantingham (UCLA Anthropology)
George Tita (UC Irvine Crim)
Martin Short (Georgia Tech Math)
Matthew Valasik (LSU Crim)
Jeremy Carter (IUPUI Crim Justice)
Rajeev Raje (IUPUI CS)