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Data Spotlight: LAPD Crime Data Analysis - A Journey from 1988 to the Present

By Greg Ridgeway posted 26 days ago

  

Undertaking research that spans over decades can present unique challenges, as was the case for my colleague, John MacDonald, and me. Our focus was on evaluating the impact of the Los Angeles rail transit system's development between 1990 and 2012 on neighborhood crime rates near the newly established transit stations.

One significant hurdle we encountered was accessing crime data prior to 2005, which was not available in digital format. Our search led us to the Los Angeles Public Library, where we discovered extensive records in the form of large books filled with quarterly crime statistics, organized by type and LAPD reporting district—the geographic units LAPD uses to segment the city. These books provided a visual testament to the city's historical crime data, featuring rows upon rows of detailed figures. Here’s a look at part of one of the pages from 1990.

Example image from a 1990 LAPD crime count


To digitize this, we assembled a team that meticulously scanned over 2,300 pages. Through the use of OCR we digitized all the tables and verified the accuracy of the data against each page’s margin totals—a relief, as every page included these crucial figures. This painstaking process resulted in a comprehensive dataset, spanning from 1988 to 2004, encompassing quarterly crime counts across 17 crime categories for each reporting district.

With the advent of the Los Angeles open data portal (data.lacity.org) in 2010, accessing complete incident-level data became significantly more straightforward. However, our journey included navigating changes in the LAPD's district boundaries and numbering systems over the years. We acquired historical maps, aligning all data with the 2005 reporting district configurations to ensure consistency.

Our analysis, detailed in our publication "Effect of Rail Transit on Crime: A Study of Los Angeles from 1988-2014" (Ridgeway & MacDonald, 2017), revealed that the rail transit system's expansion did not significantly impact crime rates in adjacent neighborhoods. This dataset also enabled us to explore another critical aspect of Los Angeles crime policy: the efficacy of civil gang injunctions. Our findings indicated that the implementation of 46 gang injunctions between 1993 and 2013 led to a short-term crime reduction of 5% and a long-term decrease of 18%.

The wealth of data we compiled not only answered pivotal policy questions but also opened the door for further research into the effects of various policies on Los Angeles crime over decades. We encourage researchers and policymakers alike to utilize this dataset, which includes both the cleaned data and the original scanned pages, along with early reporting district maps. These resources are freely available for academic and policy analysis, providing a foundation for continued exploration of crime and policy impacts in Los Angeles.

For further insights and to access the dataset, visit https://github.com/gregridgeway/LAPDcrimedata.

G. Ridgeway and J.M. MacDonald (2017). “Effect of Rail Transit on Crime: A Study of Los Angeles from 1988-2014,” Journal of Quantitative Criminology 33(2):277-291.

G. Ridgeway, J. Grogger, R.A. Moyer, and J.M. MacDonald (2019). “Effect of Gang Injunctions on Crime: A Study of Los Angeles from 1988-2014,” Journal of Quantitative Criminology 35(3):517-541.

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