The U.S. home ownership rate posted another increase, reaching 64.3 percent in the second quarter, up a tenth of a percentage point from the first quarter, the Commerce Department reported this week. The rate has increased 0.6 percentage points over the past year.

Younger Americans, specifically those under the age of 35, are behind most of the recent increases in the ownership rate. The home ownership rate of this younger buyer group increased to 36.5 percent in the second quarter, up 1.2 percentage points from a year earlier.

Despite the overall increase in the second quarter, the home ownership rate still remains far below its peak of 69.2 percent in late 2004.

Some economists are skeptical whether the home ownership rate will continue its recent climb. Sales of existing homes dropped 2.2 percent in June, and sales of newly built homes also dropped in June compared to the previous month, according to the National Association of REALTORS® and National Association of Home Builders. Low inventories of homes for-sale, higher home prices, and higher mortgage rates are all keeping an unseasonal lid on home sales this summer. Existing-home prices have surged 5.2 percent over the past year to a record high in June, NAR reports. The 30-year mortgage rate has increased more than half a percentage point since early January to 4.54 percent, according to Freddie Mac.

“Home ownership has bottomed out, but is likely to go more or less sideways for the foreseeable future,” Mark Zandi, economist of Moody’s Analytics, told The Wall Street Journal. “Easing credit standards and a strong job market will support home ownership, but higher mortgage rates and the change in the tax law weigh on it.”

Sales of newly built single-family homes plunged to an eight-month low last month at a time when sales should be at their highest points of the year. New single-family home sales dropped 5.3 percent month-over-month in June to a seasonally adjusted annual rate of 631,000, the Commerce Department reported Wednesday. This marks the lowest monthly annualized sales pace since October 2017.

Builders say ongoing supply constraints are being exacerbated by recent tariff disputes, which are raising the costs of building materials. In April 2017, the Trump administration imposed anti-subsidy duties on imports of Canadian softwood lumber. Builders have said that move has significantly raised the cost of building a new home.

“Uncertainty caused by tariffs and the talk of trade wars are making home buyers more cautious, and builders are taking note of this situation,” says Randy Noel, chairman of the National Association of Home Builders. “Not only are consumers and builders concerned about the current lumber tariffs but also the next round of proposed tariffs on a number of goods and services.”

The median sales price of new homes dropped to $302,100 in June, 4.2 percent lower than a year prior. “That prices were lower likely shows the dominance of homes sold in the South—where prices are lower—than a lack of demand,” Robert Frick, corporate economist for Navy Federal Credit Union in Vienna, Va., told Reuters.

While new-home sales under performed in June, the builders’ trade group still sees “solid demand for new-home construction.” New-home sales were up in the first half of 2018 and remain 6.8 percent higher on a year-to-date basis compared to last year, says Robert Dietz, NAHB’s chief economist.

But a shortage of new construction persists. In June, the stock of new homes rose to a nine-year high of 301,000 units, but supply is still just over half of what it was at the peak of the housing boom in 2006.

Downsizing baby boomers who are leaving home ownership behind may send shock waves throughout the real estate market, two new studies warn. “Home ownership demand from younger generations is insufficient to fill the void left by multitudes of departing older owners,” according to Fannie Mae’s Economic Strategic Research group. A separate study by the Stephen S. Fuller Institute at George Mason University says the significant number of older owners in relatively large homes in the Washington, D.C., market may lead to a “baby boomer sell-off” that could be mirrored in others parts of the country.

Baby boomers—those born between 1946 and 1964—own two in five homes in the country. The generations following them occupy only about 14 million homes.

Eventually, health or other issues will force baby boomers to move. Between 2016 and 2026, as many as 11.9 million older owners will end their home ownership status, according to estimates by Fannie Mae. From 2026 to 2036, another 13.1 million to 14.6 million will move as well.

Researchers in the Fannie study warn that this generational unloading of homes could be “negative for the home sales market.” Upcoming generations may not have the desire or be unable financially to buy the homes baby boomer are leaving behind. But it’s impossible to forecast price impacts 10 years ahead, Dowell Myers, a professor at the University of Southern California, told real estate columnist Kenneth R. Harney. “We do not mean to be alarmists,” Myers says, while noting that he hopes the issue will prompt more consideration for public and private policies that may cushion the potential fallout. He points to financing programs, for example, that could help urge more millennials to buy their first homes.

Lawrence Yun, chief economist with the National Association of REALTORS®, is not predicting such doom and gloom as a result of a baby boomer sell-off. He cites population growth in the U.S. and emphasizes the rising importance of foreign-born buyers. There should be “no measurable declines” from baby boomers, he says.