David Friedman uses the focus on affordable housing to illustrate how asking the right questions can lead you to different conclusions than you would otherwise get.
When someone moves into one house he moves out of another, which is then available for someone else to move into. If the development is built and the units are bought by people currently living in San Jose, the net result will be to increase the city's housing stock by almost a thousand units. Doing that will make more housing available in the city and lower its cost. The question the Mayor should be asking, assuming that what he is really interested in is the welfare of the citizens of the city and not merely his ability to control things, is whether the development will draw mostly from current residents or mostly from people who would not otherwise live in the city. Pretty clearly, that question never occurred to him.
The assumption of the Mayor–I think of city planners more generally–is that the way to get affordable housing is to build affordable housing. That is not the only way of getting it. The alternative, very common in the history of U.S. cities in the past, was for poor people to move into housing that had been occupied by, possibly built for, less poor people, vacated when the less poor people moved into newer and better houses.
The same way poor people get cars.
I thought this was very insightful.