In a recent paper co-authored with Harvard Kennedy School PhD candidate Lauren Russell, Daniel Shoag, a Kennedy School and Case Western Reserve professor, found “a significant relationship between land-use restrictions and fertility rates across all measures and geographies.” Shoag and Russell determined the relative restrictiveness of a city’s land-use policies by the number of cases brought to court around housing issues; they crossed that data with listings like the Wharton Residential Land Use Index to arrive at a complete picture of a city’s zoning codes and housing stock. When overlayed with fertility data from the CDC, they found that the cities and towns that actively stifle or restrict development are seeing fertility rates, especially among young women, plummet.