Commuting, by and large, stinks. Congested roads can quickly turn what would be a scenic drive into a test of patience, and for those who use mass transit, the decision to put their trips in the hands of local public-transit systems can quickly go from freeing to aggravating thanks to late trains, crowded buses, or the bad behavior of fellow riders. But lengthy and burdensome commutes are awful for another reason, too—they disproportionately affect the poor, making it more difficult for them to reach and hold onto jobs.

A recent survey released by Citi found that on average, round trip commutes for those who were employed full time in the U.S. took about 45 minutes and costs around $12 per day. But for both cost and time there were enormous variations. In metro areas like New York and Chicago, average round-trip commute times were longer than an hour, and in Los Angeles the daily cost of commuting averaged about $14—that’s more than $3,500 each year. Nearly two-thirds of commuters said that the cost of getting to work had increased over the past five years, with about 30 percent saying that their cost of commuting had gone up substantially.

Most unfair of all: When it came to the most extreme commutes in terms of price, the survey found that about 11 percent of respondents who said they paid $21 or more for their daily commute made less than $35,000. For those in the highest income bracket—making $75,000 or more—only 8 percent had such pricey commutes.

Though the Citi survey included a small sample size of about 1,000 respondents, some of the issues brought up by these findings are corroborated by other recent research in this area. According to Natalie Holmes and Alan Berube of the Brookings Institution the shifting locations of impoverished populations is a major contributor to the problem. “Between 2000 and 2012, poverty grew and re-concentrated in parts of metropolitan areas that were farther from jobs, particularly in suburbs, which are now home to more than half of the poor residents of the country’s 100 largest metro areas,” they write.

Between 2000 and 2012, the number of jobs within a worker’s typical commuting distance—which can range from five miles to nearly 13 miles depending on metro area—declined by 7 percent. But for the poor and minorities, who often live in segregated, concentrated neighborhoods, that figure was much bigger: For those at the bottom of the income distribution, the decline in local job opportunities decreased by more than double what it did for the affluent. Proximate jobs for Hispanic metro-area residents has declined by 17 percent, for black residents the decline was around 14 percent. For white metro-area residents the drop was only 6 percent. That means longer, more expensive treks to work for those who need work most.

More concentrated suburban poverty, which is made worse by decreasing job opportunities, and longer, more expensive commutes can be seriously detrimental to social mobility, as recent studies have documented. And that’s not just bad for current residents of these impoverished communities: It also hinders the ability of their children to get to better schools, extracurricular activities, and to slowly but surely build better lives for themselves.