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I’ve written before about the severe housing cost burden for D.C. renters. More than half of the city’s renters pay more than they can afford for housing, defined as 30 percent of their income. More than a quarter spend more than half their income on housing, giving them what’s termed a severe cost burden. Among the poorest category of Washingtonians, those making under 30 percent of area median income, a full 84 percent have a housing cost burden, with two-thirds facing a severe burden.

But as anyone who’s ever glimpsed at house listings in the city knows, affordable housing is at least as far out of reach for people looking to buy a home. The best summation of I’ve seen of this crunch comes from a chart shared by Peter Tatian at the Urban Institute, looking at a few sample households and the percentage of for-sale housing that’s affordable to them, both across the city and specifically in the two lowest-cost wards. The data are from 2011, the latest available, but if anything the situation has only worsened since then.

Take a look:

A bit of explanation: The software developer is assumed to have one dependent child, as are the building cleaner and food service worker, while the other two households have no dependent children. These household arrangements allow them to line up with the U.S. Department of Housing and Urban Development’s definitions of high-, middle-, low-, and very l0w-income households.

Things may not appear so dire at first glance. If 1 percent of houses and condos are affordable for a full-time cleaner and a part-time food worker, that’s still a lot of houses and condos. But remember that thousands of D.C. residents in these income classes are effectively competing for those homes. That drives their prices up and makes them hard to land. Add to that the fact that upper-middle-class residents (say, a single software developer with a child) can afford fewer than half of the city’s homes and therefore turn to, and bid up the price for, houses that might otherwise be available to lower earners, and the difficulty of purchasing a home for most Washingtonians becomes clearer. And as more families turn to wards 7 and 8 for lack of options elsewhere, those two wards, at least in certain neighborhoods, are unlikely to remain cheap for long.

House image via Shutterstock; chart via Urban Institute