The Yimby movement campaigns for building dense high-rise housing convenient to public transit.

I am strongly in favor, but some rules are needed. For instance, if a project involves tearing down housing where tenants live, they must be offered space in the new building at a comparable rent. And it is wise for cities to require a good fraction of the new apartments to be offered at affordable rent — not merely 10%. If the developer balks, the city should offer the incentive of permission for a larger building.

Gentrification occurs when a housing shortage makes run-down houses in poor people's neighborhoods attractive to the not-so-poor. In a housing shortage, there are two ways for the poor people to protect themselves from eviction: resistance and jiu-jitsu.

Resistance means trying to stop the not-so-poor from moving into your neighborhood. You have to make it ugly and unappealing. If you succeed, that does nothing to reduce the shortage that is the motor for gentrification. You only push it off onto some other neighborhood.

Jiu-jitsu means pushing to build so much new, dense housing that the not-so-poor won't be interested in buying your home. It takes a city-wide campaign, but success helps all the poor people in the city.