The Effect of Police Use of Lethal Force on Murder Levels in American Cities Before and After Ferguson

We assess the effects of police use of lethal force on subsequent murders by victim race and armed status before and after the August 2014 death of Michael Brown in Ferguson, MO. We regress monthly murder levels on instances of police use of lethal force by race and armed status controlling for fixed effects, population, unemployment, and murders in the prior month using city-level data for 93 cities from 2013 to 2015. For 2013–2015, we find that a police lethal force incident predicts a 1.8% increase in murders 2 months following the incident. However, prior to Ferguson, a police lethal force incident increases murders by 4.5% (after 2 months) and we are unable to find any evidence of differential responses to police use of lethal force based on victim race. However, we find evidence of differential responses to police use of lethal force based on victim armed status. Post-Ferguson, police use of lethal force is associated with significant differential responses based on victim race. In addition, we see a shift in the aggregate-level response to police use of lethal force. Post-Ferguson, a police lethal force incident decreases the murder level by 3.8% 3 months following the incident. In addition, lethal force incident involving a non-black victim decreases the number of murders by 4.3% while an incident involving a black victim increases the number of murders by 2.1% (after a 2-month lag). Changes in policing following the events of Ferguson had a generally positive but uneven effect.     

Power at Sea: A Naval Power Dataset, 1865–2011

Naval power is a crucial element of state power, yet existing naval data sets are limited to a small number of states and ship types. Here we present 147 years of naval data on all the world’s navies from 1865 to 2011. This country-year data set focuses on warships with ship-based weapons capable of using kinetic force to inflict damage on other structures or peoples. After identifying a country’s active naval forces, we create a measure of naval power based on the aggregate tonnage of the active ships. Additionally, we create count variables for ship types such as aircraft carriers or battleships. This article introduces the country-year data, describes variables of interests for use in country-year, dyadic, or systemic studies, and suggests potential questions of interest scholars could explore using the naval power data set.