Profit margins for home sellers took an unexpected dip in the second quarter, but they continue to significantly exceed levels from a year ago. The dip may be a sign that investment returns may be declining, according to ATTOM Data Solutions’ second-quarter 2021 U.S. Home Sales Report.

In the second quarter, the typical single-family and condo sale in the U.S. posted an average profit of $94,500. That was up from $90,000 in the first quarter and $60,575 from the second quarter of 2020. But the profit margin—the return on investment that sellers made on their original purchase price—declined from 48.4% in the first quarter of this year to 44.9% in the second quarter, ATTOM Data Solutions reports.

That drop marked a “rare decline during a time of year that usually produces some of the best returns for sellers,” the report says. “The last time typical returns on investment dropped nationally during any second-quarter period was in 2008.”

Also unexpected, the drop in profit gains comes as the national median home price surged to another record in the second quarter of $305,000, ATTOM Data Solutions reports, up 22% compared to a year earlier.

“Still, profits dropped in the second quarter of this year because price gains—high as they were—were smaller than increases that recent sellers had been paying when they originally bought their homes,” the report notes. “The gap between the latest price gains and earlier increases caused the dip in profit margins.”

Profit margins dropped year over year in 37 of 195 metro areas analyzed but declined quarterly in 86—or 44%–of the metros, the report notes. The largest annual decreases were in San Jose, Calif. (margin down from 85.6% in the second quarter of 2020 to 67.4% in the second quarter of 2021), followed by Las Vegas (down from 45.8% to 30.5%); Kansas City, Mo. (down from 41.4% to 26.5%); Myrtle Beach, S.C. (down from 26.6% to 11.7%); and Los Angeles (down from 55.7% to 41.3%).

“Prices and profits from the second quarter painted yet another picture of a housing market in high gear—except for one thing,” said Todd Teta, chief product officer at ATTOM. “Profit margins dropped in the second quarter, which is very unusual for any springtime period because that’s when the housing market is usually hottest or close to it. While it may just be a momentary thing in today’s volatile market, it’s definitely something to keep an eye on in case it’s a sign that the market is finally cooling or giving in to some of the economic forces connected to the virus pandemic.”

In the second quarter, the largest annual increases in profit margins occurred in Boise City, Idaho (up from 59.6% in the second quarter of 2020 to 124.3% in the second quarter of 2021), followed by Charlottesville, Va. (up from 202.% to 83.6%), Scranton, Pa. (up from 34.9% to 80.9%), Claremont-Lebanon, N.H. (up from 18% to 57.3%), and Bellingham, Wash. (up from 60.8% to 98%).