When you read up on U.S. political basics, you can’t help but come across the detail that many of the people in cities in the U.S. seem to lean left, yet what isn’t as clear is why and what influences their concentration in cities/urban areas.

Cities don’t exactly appear to be affordable, and left-leaning folks in the U.S. don’t seem to necessarily be much wealthier than right-leaning folks, so what’s contributed to this situation?