Back in 2010, the U.K. set up a seven-person "Nudge Unit" inside government to begin applying behavioral science to public policy and programs. The group specialized in making small tweaks that often yielded meaningful and measurable results, whether it involved reminding people to pay their taxes, helping them find jobs, or encouraging them to be organ donors.

Twelve years later, a number of U.S. city halls have essentially created nudge units of their own. In some cases, this capacity is formalized within dedicated teams drawing direct inspiration from the U.K. experience. In other cases, it's more informally driven by individuals who've become in-house experts in behavioral science. Either way, these cities are trailblazing a new frontier for local government when it comes to using evidence to deliver better results for their residents.

For most U.S. cities, exposure to this way of working started with their involvement in What Works Cities, a Bloomberg Philanthropies initiative that helps city leaders use data and evidence better. Through the initiative, many cities have learned and run experiments with the original Nudge Unit, which spun off as a social purpose company called the Behavioral Insights Team, or BIT.