"Filtering"

A trickle-down theory that suggests upzoning creates a “ripple effect” — as higher income residents move into the new housing created by increased density, their vacated older homes or apartments would sell or rent for less, thereby driving down the prices for lower-income residents. This is a central tenet of those who believe that the solution to affordability is simply to increase housing density and new construction. The theory is that, with more new construction, available housing “‘filters’ down as wealthier households move to newer units, leaving older homes available to the less wealthy.”