Murder rates tend to follow high poverty census tracts. In good income areas of the US, murder rates tend to be extremely low, meaning <3/100K, in high poverty area they can reach 40/100K. Detroit, because of the depth of the middle class exodus after 1970, had the unfortunate fate of being a city that became almost uniformly poor, so the net numbers for the city really represented the very high percentage of high poverty census tracts as proportion of the total. e.g, Murder on the South Side of Chicago was always as bad as the rough parts of Detroit but Chicago still had a lot of non-poverty areas to balance out the city wide totals. The drop in Detroit's numbers just reflects economic recovery in more parts of the city now. Employment solves a huge number of other problems.