Though millennials often get a bad rap for clinging to rental housing and stubbornly refusing to jump into homeownership, a study released Wednesday by Harvard University's Joint Center for Housing Studies suggests more than half of renters are actually in their 40s or older.

The study – which extensively details the rental and homeownership trends that have played out in America over more than a decade – challenges the notion that young people are mostly to blame for staggeringly high rental occupancy and historically low homeownership rates across the country. It also casts doubt on whether the housing market has truly recovered from its collapse in the mid-2000s, with so many atypical renters staying away from traditional homeownership.

"In mid-2015, 43 million families and individuals lived in rental housing, up nearly 9 million from 2005 – the largest gain in any 10-year period on record," the report said. "While households in their 20s make up the single largest share [of renters], households aged 40 and over now account for a majority of all renters."

Those younger than 30 account for nearly 26 percent of America's rental market, according to the study. That's far larger than any other age demographic's share. But the number of households rented to people younger than 30 has only expanded by about 1 million units over the last 10 years.

For comparison's sake, the number of units rented to people in their 50s ballooned by more than 2.3 million over the same window, while those occupied by people in their 60s climbed by more than 2 million. Those older than 50 years old accounted for 55 percent of the growth in America's rental population between 2005 and 2015, compared with those under 30, who accounted for just 11 percent of the gains.

"This growth reflects the aging baby boomer renters (born 1946-1964), as well as declines in homeownership rates among this generation," the report said. "While the conventional image of renters is groups of young, unrelated adults living together, these types of non-family households make up a relatively small share of all renters, and their numbers have grown only modestly in the past 10 years."

Overall, the more than 22 million units rented to people at least 40 years of age now account for 51 percent of the country's rental market, according to the study. Back in 1995, that share was less than 43 percent.

And that demographic shift is taking a bite out of the housing market. The seasonally adjusted national homeownership rate in July, August and September sat at just 63.5 percent, which tied the second quarter of this year for the lowest rate on record dating back to 1980, according to the Census Bureau. Rental vacancy rates, meanwhile, are now "at their lowest point since 1985," according to the Harvard study.

Part of the problem could be tighter credit standards that limit how many people are approved each year for mortgage loans. Though mortgage denial rates fell last year and have been respectable so far in 2015, application standards are still significantly more stringent than they were a decade ago.

"It is extremely unlikely that we'll get back to the credit conditions that prevailed in the 2004 to 2007 period of time, but that's probably a good thing," Stan Humphries, chief analytics officer and chief economist at Zillow, told U.S. News earlier this year. "I think most analysts agree at this point that credit conditions were too loose at that point in time."

Overall, though, people are now less likely to own a home than they were a decade or two ago, which hurts the real estate market and ultimately drags on consumers' capacity for spending. That's despite the fact that monthly rental fees in much of the country are actually more expensive than mortgage payments would be. Housing research site Trulia estimates buying a home in the U.S. is 36 percent cheaper nationally and is the more affordable choice in all of the country's 100 largest metropolitan regions.

However, high rental costs have complicated millions of consumers' ability to save up for a down payment on a home, effectively trapping them in a vicious cycle. The Census Bureau in the third quarter reported the median monthly rent for a vacant apartment in the U.S. was $802. That's virtually unchanged from the second quarter, when rental costs climbed to an all-time high of $803.

A recent uptick in building permits and construction related to multi-unit facilities like apartment buildings has been hailed as a sign that rental prices could soon ease. The idea is rooted in basic supply and demand functions. If demand is high and supply is low, landlords can ratchet up asking prices. But if more units spring onto the market, landlords will have more competition to fill their vacancies and could be forced to lower (or at least moderate) what they charge tenants.

But the Harvard study says the median monthly rental price of a newly constructed market-rate apartment last year hit nearly $1,400. That's up 26 percent from just 2012 and is significantly higher than what most lower-income renters can reasonably pay.

"Indeed, only 10 percent of newly constructed units had asking rents under $850, a level that about half of all renters could afford," the report said. "For the roughly 1 in 5 renters earning less than $15,000 annually, rents would have to be under $400 to be affordable. Between 2003 and 2013, new construction added only 5 percent to the stock of housing at these levels."

The bottom line here is that higher rental costs are increasingly limiting consumers' ability to spend on a home or other would-be purchases, which inherently drags on America's consumer-driven economic growth.

Nearly half of all renters last year (49.3 percent) spent more than 30 percent of their annual income on housing alone, according to the study. More than a quarter spent more than half of their income on housing.