This Atlantic Cities piece measures which metro areas are the easiest for middle-income folks to buy homes in. They define this by the fraction of homes that the median earner in the city could buy, assuming this earner stays within sensible limits for what he spends on a home. That is, the earner is expected to spend 31% or less of his income on a home. I never know whether the 31% number there refers to gross or net. Again, people often make the mistake of considering their homeownership decision outside the context of the rest of their finances. You want your whole financial picture, including retirement savings and so forth, to be healthy, not just your homeownership picture.

But setting that aside: by this measure, Boston is not very affordable. If you take even the looser standard of the fraction of homes that are affordable if the head of household (love that Victorian label) has a college degree, then Boston ranks 93rd out of 100.

Consistent with my impression, Pittsburgh is 45th, and Detroit is 17th. This gets at something: you really want to measure along two axes. Along the x-axis, measure affordability; on the y-axis, measure desirability. Detroit is affordable but not desirable. The Bay Area, let’s say, is desirable but not affordable. What one wants is the set of cities that are both affordable and desirable. Or maybe, within the set of desirable cities, one wants to maximize the amount of desirability from the marginal dollar. (You’d want to limit to desirable cities to avoid Detroit showing up on the list. If you’re willing to consider the possibility of living in Detroit, perhaps you can relax this in the thought experiment.)

I don’t know how one would measure desirability. Basically you’d measure it by how many people want to live there. But the only way you can measure that is by how many people *do* live there or *have* tried to move there. The price of housing is a decent measure of those things. But the price of housing measures the intersection of demand with supply, and supply is controlled by regulators. So I can’t think of how to measure desirability.

It’s odd, though, that Pittsburgh may well end up maximizing the combination of desirability and affordability.