[21echoes]

re: 2, this is covered quite clearly in the abstract: "There is no relationship between county-level racial bias in police shootings and crime rates (even race-specific crime rates), meaning that the racial bias observed in police shootings in this data set is not explainable as a response to local-level crime rates."

[chvid]

Why does it have to be explained at "county-level"?

[21echoes]

If it's true at the county-level, it's true at the national level (which is also stated in the abstract). By specifying it's additionally true at the county level, it makes a much stronger claim -- that high racial bias does not exist only in high-crime areas, and as such, racial bias is not explainable by crime rates.