Two new studies describe a challenge facing senior living operators trying to attract older adults into their properties: seniors are holding onto their housing rather than downsizing because their adult children are still living with them.

The Pew Research Center says that in 2014, for the first time in more than 130 years, adults aged 18 to 34 years were more likely to be living in their parents’ homes than in their own households with spouses or partners. Mostly, according to Pew, it’s because members of what is known as the millennial generation are postponing marriage or not marrying at all, or they are having a difficult time finding a job or finding one that pays well enough for them to move out.

Other research, by real estate brokerage Redfin, found that one-fifth of homeowners aged 55 to 64 years still have adult children living with them at home. This phenomenon means that many baby boomers (aged 51 to 70 years) are not able to sell their family homes and downsize for retirement, Nela Richardson, chief economist at Redfin, told the Associated Press.