A set of formulas are presented for the measurement of attraction of urban centers of convergent migratory movement, and for the measurement of the mobility of local population, based upon observations of actual migratory movements. By this method, the author found the following order of cities in a scale of attraction of urban centers to graduate physicians: Los Angeles, New York, Chicago, Minneapolis-St. Paul, Detroit, St. Louis. (PsycINFO Database Record (c) 2006 APA, all rights reserved)