Disparity Does not Mean Bias: Making Sense of Observed Racial Disparities in Fatal Officer-Involved Shootings with Multiple Benchmarks

There has recently been much discussion in the United States on racial disparities in police officer-involved shootings (OIS). Comparing the fraction of black citizens who were fatally shot to their fraction of the general US population, many claim that there is racial bias in police officers’ decisions.

However, this is not necessarily a correct conclusion to draw, since the population at risk of being fatally shot may not be the same as the general US population. If most of the population does not encounter the police in any given year, there is little to no chance of them being fatally shot by police, except in cases of ricochet or non-purposeful shooting, which are very rare.

In order to actually calculate racial disparity, the comparison benchmark should be a group of people who have a chance of being involved in a fatal OIS in the first place. In terms of social science research, this group of people is similar to the at-risk population for a disease or symptom, against whom the actual rate of people affected are compared. Determining a benchmark population to properly estimate the population that is ever at risk of being involved in a fatal OIS is a difficult problem, but is invaluable to properly assessing the racial disparities in OIS situations.

In 2017, a group of researchers used seven different benchmarks for the at-risk of fatal OIS population, and found varying levels of racial disparities in fatal OIS across the US, using data from 2015-2017. Their study shows the importance of selecting the appropriate benchmark for conclusions to be drawn from. It also notes the assumptions that are made with the different benchmarks, and why those are necessary to be aware of when calculating disparity and making inferences about its meaning.

The formula used to find the odds ratio of a black citizen being fatally shot as opposed to a white citizen being fatally shot was simply the black fatality rate over the white fatality rate, or:

[Black Fatally Shot ÷ Black Benchmark]

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[White Fatally Shot ÷ White Benchmark]

 

Using publicly available data from the U.S. Census for the first benchmark, data from the Police-Public Contact Survey for benchmarks 2-4, and data from the Uniform Crime Report for benchmarks 5-7, the researchers compared data from the Washington Post’s fatal OIS data to calculate the impact a person’s race (black or white) had on the likelihood of being fatally shot by an officer compared to the at-risk population.

They found that the odds ratios varied greatly, with results across all three years (2015-2017) for each benchmark as noted here. Results greater than 1.0 indicate that blacks are more likely to be fatally shot while results less than 1.0 indicate that whites were more likely to be fatally shot.

  • In the general U.S. population: black citizens are about 3 times more likely to be fatally shot by an officer
  • In police-initiated contacts: about 3.25 times more likely
  • In traffic stops: about 3.5 times more likely
  • In street stops: about 2.5 times more likely
  • In total arrests: about 1.3 times more likely
  • In arrests for violent crime: about 0.8 times as likely
  • In arrests for weapons offenses: about 0.67 times as likely

The results show that in the first five benchmark cases, black people are more likely to be killed in a fatal OIS, but with very different likelihoods, whereas in the last two cases, white people are more likely to be killed in a fatal OIS. For interpretation purposes, results can be grouped into those greater than 1.0, indicating situations where black people are more likely to be fatally shot, and those less than 1.0, indicating situations where white people are more likely to be fatally shot.

The assumptions being used to craft these benchmarks include: OIS occur in response to perceived imminently dangerous citizen behaviors, criminal behavior is a reasonable proxy for imminently dangerous behavior, and arrests are a reasonable proxy for criminal behavior. By that logic, people should be comparing the fatal OIS rate to one of the other benchmarks which take into account the population among whom an OIS has a chance of happening in the first place. Essentially, if the opportunity of an OIS is not even an option, that case should not be used to tell whether or not the officer was more likely to fatally shoot someone based on their race.

The researchers acknowledged some limitations of their study, including the difficulty of getting accurate data from all law enforcement agencies, especially as the government does not track much of the OIS-related data, though hopefully they will begin doing so soon. Since the data being used is collected at the national level, these results cannot be used to infer anything about a more specific group, such as an individual case, a single department, or county law enforcement offices.

The study specifically focused on the racial disparity between black and white citizens who are fatally shot by officers. This data does not consider non-lethal interactions with the police, and so cannot be used to find anything about those cases. Since they only measure the racial disparity among fatal OIS, the results also cannot be used to determine anything about disparity or potential bias that may occur before the chance of an OIS, such as any disparity or bias by officers when stopping people for traffic stops or street stops. Finally, this data cannot be used to show that racial bias is the driving force behind any uncovered racial disparities.

This study also does not deal with cases when the at-risk group being used as the benchmark does not always encompass all the situations in which a fatal OIS may happen, such as the controversial cases of officers shooting and killing citizens who posed no imminent threat. The researchers mention that these scenarios complicate the use of certain benchmarks that do not take these situations into account.

Overall, the study emphasizes the importance of choosing a benchmark population against which to compare the rate of people who are fatally shot by officers. Because many people do not encounter the police and many police interactions occur with no force, let alone lethal force, ever being used, the benchmarks for finding racial disparities must be more carefully considered before being used to determine bias.

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Takeaway:

  • The comparison benchmark for fatal OIS should include those who have a chance of being fatally shot by police, instead of the entire general population
  • Black people are more likely to be shot and killed in OIS in police-initiated contacts, traffic stops, street stops, and total arrests
  • White people are more likely to be shot and killed in OIS in arrests for violent crime and in arrests for weapons offenses
  • Benchmarks for determining racial disparity must be carefully considered before being used to determine bias

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Reference:

Brandon Tregle, Justin Nix & Geoffrey P. Alpert (2018): Disparity does not mean bias: making sense of observed racial disparities in fatal officer-involved shootings with multiple benchmarks, Journal of Crime and Justice, DOI: 10.1080/0735648X.20181547269

 

 

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