For the last generation, Mexican migration to the United States has been one of the strongest factors driving neighborhood change, labor markets, and housing demand in American cities from California to New Jersey. Now the Times has a report, riffing off of research by Princeton’s Douglas Massey, that suggests that the long era characterized by heavy migration from Mexico may be coming to a close. If the trend is real, it will be interesting to examine how U.S. urban development is influenced by this change over the next several years.