US President Donald Trump has said he will move to ban big corporate investors from buying single-family homes, in a bid to make housing more affordable for Americans.

In a social media post on Wednesday, Trump said he would ask Congress to “codify” the plan and would discuss it further at the Davos World Economic Forum later this month.

The pledge bolstered an idea that has been circulating for years among housing advocates and lawmakers, in response to Wall Street’s increased role in America’s residential housing market. But some analysts question the extent to which a ban would affect prices.

Shares of Blackstone, one of the largest private equity buyers, fell more than 5% on Wednesday.

“That American Dream is increasingly out of reach for far too many people, especially younger Americans,” Trump said on social media, referring to home ownership.

“People live in homes, not corporations.”

The White House did not immediately respond to a request for comment on the details of a possible ban, including whether it would require congressional approval.

Trump’s comments on Wednesday come as his administration faces growing public pessimism about his handling of the economy. He has in recent weeks sought to allay voter anxiety about the cost of living in the US, with home affordability high on the list of Americans’ concerns.

Sam Garin, a spokesperson for an advocacy group that has raised alarm about the effect of private equity ownership on renters, said her group welcomed Trump’s move.

“We eagerly await the details of what this policy will actually entail,” said Garin, of the Private Equity Stakeholder Project, adding: “But we urge policymakers not to stop there.”

Since the 2008 financial crisis led to a wave of foreclosures, Wall Street investors such as Blackstone and other private equity firms have bought tens of thousands of homes to rent out, becoming major landlords, especially in certain markets.

Their role has drawn scrutiny from lawmakers in both political parties, who have blamed the firms for helping to push up the cost of renting and buying.

On Wednesday, Ohio Republican Senator Bernie Moreno, said he would introduce legislation to codify Trump’s proposal.

Shares of property firms fell on Wednesday after Trump’s comments. Builders FirstSource, a building products supplier, dropped more than 5%, while Invitation Homes, which owns single-family homes, fell 6%.

But some housing industry analysts questioned whether a ban would make much of a dent in home prices, given the relatively small role of institutional investors in the overall market.

Laurie Goodman, a fellow at the Urban Institute, said the impact of a ban would depend in part on how “large” investors are defined.

Blackstone has said that institutions own 0.5% of all single-family homes in the US.

Goodman said that her research found that institutional investors, when defined as those that own at least 1,000 units in three or more locations, own about 4% of the single-family market.

That number, she added, has held steady over the past few years, as purchases have slowed amid high interest rates and high home prices.

Goodman said a proposal for a ban raised other questions, such as how existing properties owned by institutional investors would be handled.

She said instead of an outright ban, “institutional investors should be required to provide more for their tenants”.