Here's some hard, albeit narrow, data on the tendency of young kids to move downtown but keep their official address in the burbs.

http://bridgemi.com/2013/03/auto-rat...s-into-hiding/

Alok Sharma analyzes data for a living. In 2010, he had a client, a politician, who was running for office and wanted to know if it was worth his time to campaign door-to-door in Detroit’s high-rise apartment buildings. Sharma thought the answer might be found by running a high-rise address through the Qualified Voter File, a public document of every registered voter in Michigan. He chose his own: the Kales Building, with 18 floors overlooking Grand Circus Park and 116 one- and two-bedroom apartments.

It is, Sharma said, full of young professionals like him, as well as empty-nesters — just the type of middle-class people who are likely to be engaged, active voters. When Sharma looked, the building was fully occupied.

Yet he found only nine names in the Qualified Voter File – counting his own.
For those keeping score at home, 9 registered voters out of 116 apartments is 7.75%. The percentage goes even lower if you factor in the two bedroom apartments. Statewide, in 2012, 97.8% of voting-age individuals were registered to vote.