How do metros rank on rent affordability? It depends on what you mean by rental affordability. Experts rely on the rule of thumb that renters should spend no more than 30 percent of their before-tax income on rent and utilities. Across the nation’s 100 largest metro areas, about 54 percent of renters paid more than 30 percent of their incomes on housing in 2010, according to the American Community Survey (ACS). At the extremes, over 60 percent of renters overpaid in Miami, Orlando, Riverside, and Stockton; around 46 percent did so in Harrisburg and Des Moines. This “overpayment” index gives an estimate of what current tenants actually pay.

In a recent MetroTrends commentary, my colleague Bob Lerman reported another standard that he calls the “rent burden,” dividing the median rent plus utilities by the median income as reported by the ACS. This yields the optimistic conclusion that families at the 12th percentile of income (about $20,000 per year) can spend 30 percent or less of their income to rent a place at the 20th percentile of rents (about $500 a month). This measure doesn’t account for the real distribution of tenants across rental units, though; some higher-income renters occupy low-cost apartments and many low-income earners live in apartments renting at median levels or higher. Lerman’s index gives a rough measure of the relative cost of a metro area’s rental housing stock.

The National Low Income Housing Coalition’s “housing wage” offers another dimension for housing affordability: the number of work hours per week at the local or state minimum wage required to afford fair market rent (HUD’s estimate of fair rent in a local area). The Coalition lists work hours required for a range of apartment sizes and follows the 30-percent-of-income rule of thumb. In the DC suburbs, for example, it would take 159 hours of minimum-wage work per week to afford a two-bedroom place at fair market rent. Whereas the “overpayment” and “burden” measures use rents paid by current tenants, the “housing wage” measure is based on a survey of asking prices for vacant apartments.

The housing wage shows the costs confronting low-wage workers looking to rent an apartment. The interactive map below ranks the 100 largest U.S. metros on the three measures of rent burden. Mouse over a metro to see more information; use the slider on the right to switch between measures.

Source: Urban Institute analysis of 2010 NLHC and ACS data

Ranking the 100 largest metro areas on these three measures suggests that no single measure really captures all the subtlety of rental affordability. Some metros rank high on the overpayment scale (meaning many people pay more than 30 percent of their incomes on rent), but rank low on the housing wage measure (meaning low-wage workers have affordable rent options).The Washington, DC, metro area, for example, ranks 87th on overpayment, 40th on rent burden, and third on the housing wage measure. El Paso, at the other end of the spectrum, has the second lowest housing wage and the 11th highest rent burden, but ranks 61st in overpayment.

The alternatives for measuring rental affordability don’t even end here. Michael Stone’s 1993 book Shelter Poverty, for example, reported how much money would be left in a family’s budget—assuming a “basic” no-frills budget—after they paid for rent and utilities. Stone contended reasonably that rent and utilities usually rank at the top of families’ priorities list; those who forgo other needs, such as food or health care, to pay their housing costs are “shelter poor.” Many large families in 1990 were shelter poor but spent less than 30 percent of their income on housing, and many small and older families and those with higher incomes weren’t shelter poor even when they surpassed the 30 percent standard. We now also have the supplemental poverty measure, which accounts for housing cost differences. Once this measure can be computed for local areas, we’ll be closer to a more integrated view of how material want varies across the United States. But even then, we’ll wrestle with simple measures of rental affordability that tell only part of the story.