According to this piece in AOL Real Estate more and more adults are living with roommates due to rising rents:
Nearly a third (32 percent) of adults live in doubled-up households, or homes where two or more working-aged adults live together but aren’t married or partners. The share of doubled-up households has steadily risen over the past decade, up from 25.4 percent in 2000 and 30.8 percent in 2010.
This rise in doubled-up households coincides with rental prices that are increasingly unaffordable nationwide. Americans making the national median income ($53,216) should currently expect to spend nearly 30 percent of their monthly income on rent, the highest rate ever. Rather than moving to a smaller home or to a less expensive area, many people are choosing to live with roommates.
Not surprisingly the cities with the highest shares of households with roommates are those with high demand and low availability. Think San Francisco, New York, LA, etc.