While California tops the list of states with insane housing costs, it’s by no means a uniquely Golden State phenomenon. Building affordable housing—and particularly getting cities and other localities to permit its construction—is a tough endeavor that has bedeviled state policymakers across the country. So where should Californians look to solve a problem that feels so intractable? Affordable housing experts suggest legislators find inspiration in Massachusetts. For more than 40 years, the state’s signature affordable housing policy—Massachusetts “40B”—has served as a model for how states can motivate and sometimes bully reluctant localities into meeting their fair share of affordable housing.