by Alex Ciomek
Crime in Boston, and nationally, varies from year to year and from neighborhood to neighborhood. Given the potential for different trends over time across Boston, we adjusted crime rates according to citywide trends in order to better understand crime trajectories in different neighborhoods. We determine how the crime trajectories of individual census block groups compare to Boston’s overall crime trend from 2011 to 2018 by allowing the relationship between year and crime to vary by block group using hierarchical linear models.
In this blog post, I will illustrate how crime trends vary across the city with maps of two types of crime, social disorder and the prevalence of guns, as measured by 911 calls from 2011 to 2018. The rate of public social disorder reflects the number of events that reflect social disorder in the public space (e.g. panhandling) per 1,000 people in the population. The rate of gun prevalence reflects the number of events that involve the use of guns (e.g. shootings) per 1,000 people in the population. In both cases, yearly population counts for census block groups were obtained from the U.S. Census Bureau’s American Community Survey, using the 5-year estimates with the median year matching the year of the ecometric. For example, for 2012 measures, the 2010-2014 ACS was used. Because the most recent release was the 2013-2017 ACS, this is used for all ecometrics for years 2015-2018. Across the two maps, it is evident that only some areas of Boston have notably different, either decreasing or increasing, crime trajectories as compared to the city overall.
The map above shows the trend from 2011 to 2018 in social disorder crime rates by census block group, in comparison to the Boston-wide trend over the same time period. The areas in green are block groups that have comparably notable decreasing trajectories in their rates of social disorder from 2011 to 2018. These areas include the Boston College area within Brighton, three areas near the Fens, and a few areas throughout Jamaica Plain, Roslindale, and West Roxbury. The decreasing trend in public social disorder in these areas, as compared to Boston in general, could be due to their more residential nature, in comparison to the areas of downtown Boston and Back Bay that are more likely to have a notably increasing trend. In addition to downtown, some areas of Charlestown, the North End, Chinatown, Roxbury, and Dorchester also have notably increasing trends of social disorder crime rates in relation to Boston overall. However, more in-depth analyses would be useful in determining what factors relate to differing social disorder rate trajectories over time and whether these factors operate at the census block group level or at larger (e.g. neighborhood) or smaller (e.g. street) geographies.
The map above shows the trend from 2011 to 2018 in the prevalence of guns rates by census block group, in comparison to the Boston-wide trend over the same time period. In contrast to the social disorder trends, there are no census block groups that have notably decreasing trajectories in comparison to the overall citywide trend. This means that the majority of Boston’s census block groups have a similar trajectory in comparison to Boston as a whole. However, similarly to social disorder, there are some areas that have a comparably notable increasing trajectory in the rates of the prevalence of guns. These areas are concentrated in Roxbury, Mattapan, and Dorchester. Although these areas of Boston may be expected to have higher rates of gun prevalence given their history of high crime reports and their reputations for notable criminal activity, the map shows that the trajectory in this type of crime is statistically increasing when compared to the overall trend of the city of Boston. Therefore, these areas are particularly important in understanding Boston crime trends and the types of crime that are unique to certain areas.
As can be seen by comparing the two maps, only a few areas have notably increasing trajectories of both social disorder and prevalence of guns crime rates. Therefore, it seems that different types of crime have different trajectories over time across the city of Boston. Because gun crimes are rare overall, an area with a downward trajectory compared to the city is unlikely, whereas social disorder is much more common and clusters around business districts and similar areas. In improving crime trajectories toward the city trend, or even better than it, it is vital to consider factors that may affect types of crime differentially and address underlying issues accordingly.
For more on the 911 data, the data and documentation can be found here. For more maps of the different 911 measures by year and neighborhood (census tract), see here under the “Social Disorder and Crime” menu on the left side (http://worldmap.harvard.edu/boston/).