Likewise, 33 percent of inner-city residents were between 22 and 24 years old, up from 29 percent in 1990.

Such apps have become an integral part of the millennial mating game.

Nationally, just 10 percent of 20- to 24-year-olds registered with an online matchmaking service in 2013, according to a Pew Research Center analysis.

She had just come out of a relationship and was unimpressed by the online matchmaking sites she tried.

She launched the League in 2015; its tag line is “Meet.

Dating apps “help you find exactly what you want,” says Tyler Cowen, an economist at George Mason University who has broached the topic on several occasions on Marginal Revolution, a popular blog he co-hosts.

Now, “you marry a college professor across town, a lawyer in D.

The services are facilitating unions between educated, affluent millennials who are clustering in such cities as San Francisco and New York.

In the process, they could be helping to intensify America’s growing income inequality, as well as wealth disparities between metropolitan areas and the rest of the country.

Those who join at no cost are entitled to three daily “prospects,” while 9 a year buys you more prospects and an assortment of other perks, such as “VIP passes” to get your friends’ membership applications fast-tracked.