The radiolab story "It's Alive" made vivid the claim of Geoffrey West and Luis Bettencourt that a city's size determines how fast people walk in that city.
West & Bettencourt have written that people earn more in large cities, waste less, file more patents, and commit more crimes -- and that city size is the main determinant of all these things.
The charming Cosma Shalizi has recently published a 15-page paper that rebuts them. From the abstract:
Re-analysis of the gross economic production and personal income for cities in the United States, however, shows that the data cannot distinguish between power laws and other functional forms ... and that size predicts relatively little of the variation between cities.
The striking appearance of scaling in previous work is largely artifact of using extensive quantities (city-wide totals) rather than intensive ones (per-capita rates).
(Sorry if that's hard to read. Horizontal axis = log( city population ). Vertical axis = pedestrian speed in m/s, give or take a standard dev. Solid & dashed lines are two fits proposed by Bettencourt & West.