I did a scatter plot of all of them and there's a bit of a trend, but for the most part it's just a mess:

http://mikeash.com/tmp/screenshot_19EB61AA-4DD0-4258-A5D5-A8...

For some reason their two tables don't include the same cities, and the numbers don't quite match up. Doing the same thing from the first table, which includes more cities, produces this:

http://mikeash.com/tmp/screenshot_C047DD43-3029-47E5-901C-9E...

There is a bit of an upward trend there, but it looks pretty uncorrelated to be.