How Many Killings by Police?

"The problems encountered by observers seeking to determine the volume of police killings in the United States are an important issue in 2016 for two reasons. First, the numbers killed by police are an obviously important indication of how large a problem police use of lethal force is in the United States. Without a reliable measure of the national pattern, how can we estimate how problematic such killings are when compared to other aspects of American crime and violence? There is also no way to estimate the relative magnitude of police killings in the United States compared to rates in other nations unless there is a reliable count of killings in the United States."