The inequality data here comes from an annual analysis Berube and Holmes conduct comparing the incomes households earn at the 20th and 95th percentile in large American cities. This year, they also looked at the cost a household would pay to rent a home at the 20th percentile of rental units in each city. Then they compared that cost (for instance, $10,286 a year in Washington) to what families earn at the 20th percentile of incomes.
As a rule of thumb, you shouldn’t spend more than 30 percent of your income on housing. So if families in the 20th percentile by income have to spend more than that to get a home in the 20th percentile of available rents, that’s a sign that they’re probably paying more than they can afford. Among the 97 cities Berube and Holmes looked at, poor families in the most unequal cities spend more than half their income on rent.