Is there any implication here?

Because murder rate has fallen in magnitude of orders faster than that.

It's not saying that black people cause murders, I don't think. It's an illustration of massive demographic replacement and gentrification: disadvantaged people are being pushed out. It's gone from being a poor minority community to a community with few minorities, and those that remain are of a higher economic class.

In turn, you don't have large groups of disadvantaged people milling together; you have a larger tax base for social programs and policing; etc. So it's also nonlinear.