How 'Ya Gonna Keep 'Em Down on the Farm (After They've Seen Paree)
Answer: I guess you can't. Apparently, May 23 2007 was the day scientists estimated the worlds population became more urban than rural:
There’s no big countdown billboard or sign in Times Square to denote it, but Wednesday, May 23, 2007, represents a major demographic shift, according to scientists from North Carolina State University and the University of Georgia: For the first time in human history, the earth’s population will be more urban than rural.(HT: Sullivan) In the U.S., this happened in the late 1910's. Here's a link to the song referenced in the title of this post.