I read an article about a year ago, which reported that about 10% of the black people in Chicago moved out between 2010 and 2017. And the overall population of Chicago was declining as well.
While there are problems with people responding to the census everywhere, Chicago is actually losing population, particularly the black population. Decent black people don’t want to live in that city. I’m sure the mayor can’t believe that people would move out of her city. But facts are stubborn things.
They are still voting there though! And will continue to do so long after they die.