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Power and Law

The issue of race in our society continues to dominate headlines, and remains a hotly debated topic on many college and university campuses.  I assigned the article, Chicago Police Department Plagues with Systemic Racism, to facilitate this conversation in my class.  As with stereotype threat, it is not enough to ask students whether they feel bias exists, but we must present them with facts that provide objective structure to any debate.  The article cites a C. P. D. task force report released on April 12, 2016  that “gives validity to the widely held belief the police have no regard for the sanctity of life when it comes to people of color.”  Evidence that blacks have had “disproportionately negative experiences with the police” includes:

  • 74% of the 404 people shot by C.P.D. between 2008-15 were black
  • 72% of investigative street stops by C.P.D. that did not lead to arrest in summer 2014 were black
  • 75% of people tasered by C.P.D. between 2012-15 were black
  • 46% of traffic stops by C.P.D. in 2013 were black

In order for my students to claim these statistics represent “disproportionate” negative experiences they need to also include the demographic breakdown in Chicago which is almost evenly split between black (31.7%), white (32.9%) and Hispanic (28.9%) each.

One graphic that stands out in the task force report displays an almost perfect power-law distribution, showing over 1,500 members of C.P.D. with 10 or more “complaint registers” acquired from 2007-15. Using 12,515 for the total number of officers in 2015  I entered the data into Excel (of course!) and fit a power curve to the data using midpoints for x-values. The equation y = 5E+06x^(-3.37) has an R-squared value of 0.9273.  The hallmark of a power-law distribution is the small number of values with large x-values.  There are many small earthquakes but very few measuring over 9 on the Richter scale.  In the C.P.D. graphic, we see that the majority of officers have very few complaints but there are 65 officers with over 30 complaints!

Power Law

Now Joel Best in Damned Lies and Statistics cautions us to look for confounding factors when we discover a difference between two groups, such as the data given above for blacks and whites.  It is possible that police are simply responding to areas where crime is higher, or maybe socioeconomic factors could explain the data.  I asked my students to reflect on this in the quiz below, and presented them with another graphic that I feel definitively justifies the claim of systemic bias.  See if you agree!

Q9 Chicago PD

  1. Use the Chicago PD Charged with Systemic Racism article[1] to answer the following questions:
    1. What evidence is presented to support the claim that “that people of color — particularly African-Americans — have had disproportionately negative experiences with the police over an extended period of time.” Give 3 specific pieces of evidence.
    2. Joel Best cautions us that: “When we discover a difference between two groups, it is easy to assume that the obvious difference between the groups (e.g., race) causes other differences. It is always possible that something else, some other variable actually causes the difference.” Comment on how this relates to the claim of systemic racism found in the Chicago PD.
    3. How does the following graphic impact your thoughts from part b.

Traffic Stops Chi_PD

[1] http://www.nytimes.com/2016/04/14/us/chicago-police-dept-plagued-by-systemic-racism-task-force-finds.html

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