The share of investor purchases of U.S. homes have climbed to an all-time high, a sign that rising home prices have done little to dampen demand for flipping homes or turning them into single-family rentals.

Big private-equity firms, real-estate speculators and others that buy properties comprised more than 11% of U.S. home purchasers in 2018, according to data released on Thursday by CoreLogic Inc.

The investor purchases are the highest on record and nearly twice the levels before the 2008 housing crash. The investor interest poses a challenge for millennials and other first-time buyers who are increasingly looking to buy starter homes and are forced to compete with deep-pocketed cash buyers.

Big commercial property owners like Blackstone Group LP and Starwood Capital Group began buying thousands of homes out of foreclosure during the housing bust. Many economists credit investors with helping to stabilize the housing market in 2011 and 2012 by buying with cash when prices were low and mortgage credit froze.

But analysts expected those purchases to slow, as the market rebounded and properties could no longer be had for fire-sale prices.