Well, as are most things in life, even in science before they are checked out -- they start as observations.<p>The important thing is whether it serves well as a predictor.<p>If we were that interested we could do a scientific analysis, counting coffee shops and chicken places in different urban areas, averaging incomes, checking trends etc.<p>But since it&#x27;s not that important to most of us, we can just use it as a kind of gauge of where things are going, and judge for ourselves if it has merit or not. Might help someone make a few bucks by buying property in the right area (although the most succesful of tose people already use this and a ton of other metrics, plus insider knowledge of future municipal plans etc).