# Recent Publications

### Counterevidence of crime-reduction effects from federal grants of military equipment to local police

In 2017, the Trump Administration restored local law enforcement agencies’ access to military weapons and some other types of surplus military equipment (SME) that had been prohibited by the Obama Administration. The Justice Department background paper used to justify this decision cited two papers published by the American Economic Association. These papers used SME data collected with a 2014 Freedom of Information Act request and concluded that SME, supplied to local law enforcement by the federal government via the 1033 Program, reduces crime. Here we show that the findings of these studies are not credible due to problems with the data. Using more detailed audit data on 1033 SME, we show that the 2014 data are flawed and that the more recent data provide no evidence that 1033 SME reduces crime.

### Do Officer-Involved Shootings Reduce Citizen Contact with Government?

Police use of force bears on central matters of political science, including equality of citizen treatment by government. In light of recent high-profile officer-involved shootings (OIS) that resulted in civilian deaths, we assess whether, conditional on a shooting, a civilian’s race predicts fatality during police-civilian interactions. We combine Los Angeles data on OIS with a novel research design to estimate the causal effects of fatal shootings on citizen-initiated contact with government. Specifically, we examine whether fatal OIS affect citizen contact with the municipal government via use of the emergency 911 and nonemergency 311 call systems in Los Angeles. We find no average effect of OIS on patterns of 911 and 311 call behavior across a wide range of empirical specifications. Our results suggest, contrary to existing evidence, that OIS, in and of themselves, do not substantively change civic behavior, at least not citizen-initiated contact with local government.

# Working Papers

### Are Police Racially Biased in the Decision to Shoot?

We present a theoretical model predicting racially biased policing produces 1) more use of potentially lethal force by firearms against Black civilians than against White civilians and 2) lower fatality rates for Black civilians than White civilians. We empirically evaluate this second prediction with original officer-involved shooting data from eight local police jurisdictions from 2010 to 2017, finding that Black fatality rates are significantly lower than White fatality rates and that this significance would survive an omitted covariate three times as strong as any of our observed covariates. Furthermore, using outcome test methodology and a comparability assumption, we estimate that at least 30% of Black civilians shot by the police would not have been shot had they been White. An omitted covariate would need to be at least three times as strong as any of our observed covariates to eliminate this finding. Finally, any omitted covariate would have to affect Black fatality rates and not Hispanic fatality rates in order to be consistent with the data.

### Estimating Bounds on Selection Bias with Outcome Tests

Outcome tests are a method for detecting bias in selection procedures using data on selected units. We use a principal stratification approach to establish lower bounds on this bias for general outcomes. We show that the Knox, Lowe, and Mummolo [2020] bound is sharp for a binary outcome, and weaken the assumptions required for that bound. We also show that the analogous bound for non-binary outcomes is not sharp and provide sharper lower bounds. We illustrate these methods with a re-analysis of the data in Anzia and Berry [2011] on the delivery of federal spending by male and female members of congress. Using Anzia and Berry [2011] data and our assumptions, we find that at least 19.9% of men elected, would not have been elected, had they been women.

### Measuring congressional gender bias from candidate to representative

For the three selection stages into the U.S. House– candidate emergence, party nomination and winning the general – we have years of research that evaluate each stage separately, with different data, different approaches and attempting to answer different questions. While this gives us a breadth of knowledge it limits our ability to compare the bias women are facing at each stage to understand where are the greatest leaks in the pipeline. Further, given incomplete attention to gender-party gaps during these stages we may be incorrectly averaging the experience across all women concealing that Democratic women and Republican women face different amounts of gender bias at different stages in the process. In order to better understand and compare the amount of gender bias Democratic and Republican women face in the process of getting elected to the U.S. House we need a single parameter that can be used at every selection stage. With an outcome test I am able to estimate the percentage of men who would not have been selected had they been women at all three stages in the process. Using Federal Elections Committee (FEC) data on campaign money raised, data from the Federal Assistance Awards Data System (FAADS) combined with data on primary and general elections I find that there is significant bias against women at every stage. While the candidate emergence stage remains a strong barrier in electing more women it is matched by significant but different within party bias in later stages. Democratic women in particular face a large amount of gender bias in the primaries while Republican women face the most bias in the general election..

### Sensitivity Analysis for Outcome Tests with Binary Data

Outcome tests are a method comparing rates of observed outcomes across selected groups to evaluate bias in decision making processes. Building on the lower bound estimand from Knox, Lowe and Mummolo [2020], I derive a lower bound in terms of relative risks and develop a sensitivity analysis to weaken the selection-on-observables assumption. Additionally I develop a covariate adjusted sensitivity analysis to assess sensitivity to unmeasured covariates. I am able to estimate a bias adjusted outcome test robust to both measured and unmeasured confounders. Applying this outcome test and sensitivity analysis to data from the Chicago Police Department (1985-2016), I find evidence for gender bias in hiring. I estimate at least 7.4% of men would not have been hired had they been women.

# Courses

### R Course Fall 2019 Schedule

September 16, 2019 Finishing up Chapter 3 of R4DS Short review: options for visualization in ggplot2: color, fill, shape, size, …

### Technology Course Day 2: R and RStudio

Installation Install R software from CRAN Install RStudio Andrew Heiss has on his blog install instructions for both Windows and OS …

# Recent Posts

### Instrumental Variables

We’ll follow along with the example used in Chapter 3 of Mostly Harmless. You can download the 1980 census from …

### Model fit and out of sample prediction

Using birthweight data from the MASS library we will work through evaluating different modeling specifications: library(MASS) # birthwt …

### Nonparametric Regression

Nonparametric Regression Given the usual conditional expectation function $E[y_i | \mathbf{x_i} = \mathbf{x}] = m(x)$ we can estimate …

### R Notes March 25, 2020

Matrices in R! We can start by creating a 3X3 matrix and filling it with the numbers 1 to 9: A <- matrix(1:9, nrow = 3, ncol = 3, …