Earlier quoted context omitted.
Supply is artificially controlled by voters who don't want density to increase, masked behind preservations, environmental concerns or just plain corruption
What changed? Governments used to aggressively intervene in the housing market.
Before 1900, the governments more or less stayed out of the details of residential housing. There were restrictions on what could be done with a piece of land, but the government generally did not get too involved in whether a single family vs multi-family apartment could be built on a specific parcel.
The 1926 SCOTUS case, Euclid vs. Ambler, changed all this. The SCOTUS ruled it was legal for cities to ban certain types of homes, such as cheaper, denser, apartments. By creating an artificial shortage of homes or by directly forbidding types of homes, the wrong type of poor minorities could be kept out of neighborhoods without officially banning them. Back then this was mainly blacks, but nowadays it’s broadened to include any type of poor minority in disfavor, such as college students.