Building new housing, even at the high end of the market, kicks off a “moving on up” effect that creates vacancy in the cheapest available homes.
*Not* building enough new housing to meet demand has the opposite effect, raising the price floor for even the worst housing.
"[Researchers found] new housing freed up older, cheaper apartments, which, in turn, became occupied by people leaving behind still-cheaper homes elsewhere in the city, and so on... The paper estimates the tower’s 512 units created at least 557 vacancies across the city."