Chicago is cracking down of dog licenses.One way to get a huge number of people to comply would be to offer low cost neutering/spaying.The price of the license could be included.This would make a serious dent in the stray population at the same time.
Stores could get into the act.If you buy $20 worth of dog food at the store you get a free dog license.If you already have a dog license,you could designate that a license could be given to somebody that could not afford one on their own.