It's like saying some cars are more responsible for a traffic jam than others, or some people on the subway contribute to it being crowded more than others. Everyone takes up space. The people who live somewhere contribute to the housing problem just like people who move in, in proportion to the amount of space they take up.

Choosing a subclass of people to scapegoat doesn't solve a structural problem.

It's also useful to think about who is doing things to make things better or worse. Moving in makes things worse, moving away makes things better. Building more housing helps, removing housing makes things worse.

So far that seems to make sense, but here's the counterintuitive part: in any given year, choosing not to move away is as bad as moving in. You're taking up space someone else could use.

(But normally we don't beat ourselves up too much for taking up space.)