I just googled it. It seems to be the mortgage lock-in effect that's the number one driving factor for lack of homes. Mortgage rates are too high so people aren't selling. They do mention construction under-building, but it's not really the main cause. Also in 2021, California passed a law allowing single family homes to become up to 4-family dwellings... oh... this lead to a bunch of companies coming in and paying cash for homes to convert to rental units. And there's actually been a lot of push to make it easier to build more and further deregulate and that seems to be having none of your expected outcomes.... because it's not really the biggest reason. And again, it has even had some of the opposite due to zoning deregulation.