more on turnout
What it means is open to lots of conjecture. But this, admitedly simplistic, look implies that turnout declined by approximately 14-15% for the Black population, but increased by 7-8% for everyone else. The divergence of those two estimates produces a pretty different mix of voters last week compared to past elections. Since 2009 was in total a pretty low turnout election to begin with, for turnout within the Black population to drop significantly below that cycle says something.
Yes, it deserves a much fuller model and I'm pondering that. I bet some variables on income, age and past voting patterns would all show up as pretty significant. Also for those who might ask, that result is unweighted on size of districts. Note that the vertical axis compares votes cast in each mayoral election, not total ballots cast technically. Some folks who showed up last week did not vote at all in the mayoral election.