Yet how do we explain the fact that these trends occurred throughout the United States in city after city, when those cities had their own mayors, their own police chiefs, and none of which did the bidding of New York?

The common belief is that the drop in crime is due to astute policing, especially to the “broken windows” theory that pointed officers toward small crimes in the belief that preventing petty lawlessness would prevent more serious crime. That approach was embraced by Giuliani and by mayors around the country. Yet many criminologists doubt those claims, and question whether different policing had much to do with the stunning drop in crime throughout the United States over the past two decades.

Outside of New York, there have also been astute mayors in many cities during these years: John Hickenlooper in Denver, Thomas Menino in Boston, Gavin Newsom in San Francisco, Wil Wynn in Austin, Shirley Franklin in Atlanta, and Richard M. Daley in Chicago. All of those cities and many more witnessed similar drops in crime along with a substantial revival in economic activity, a revitalization of decrepit neighborhoods, and an improvement in city finances and infrastructure.

You would be hard pressed to find too many commonalities in these mayors. Some adopted similar policies, but so did mayors in cities that did not fare so well, like Rochester, New York or Wichita, Kansas. Other cities also boomed in these yeas — Tulsa, Omaha, Houston, all of which benefited immeasurably from the rise of select commodities such as oil and gas in Houston and Tulsa and grain in Nebraska.

The only commonality is the influx of the same middle and professional classes that had fled many urban areas in the late 1960s and 1970s. While mayors may—may—have helped draw those classes back, it was that migration that sparked urban revival.

This influx then triggered a surge in income and the flowering of local industry or industries, notably a next wave of finance in New York and high-tech in San Francisco. Anchored by a vibrant industry, cities then attract what some have called “the knowledge class,” who increasingly propel a post-industrial America. That influx then triggered a series of cultural changes that saw sharp drops in crime and substantial improvement in the quality of life. Each city had its own specific story, its own cast of characters, but because it happened in so many places simultaneously, it is difficult to convincingly argue that these shifts happened because of who was mayor or police chief.

It is also true that the cities that have declined and gone in the opposite direction saw a continued flight of the professional classes and were often ill-served by their elected local officials. Detroit is of course Exhibit A, but even with a better local government, Detroit would have been hard pressed to stave off the immense pressure caused by the rapid changes in the auto industry, which had been the region’s lifeblood.