WASHINGTON (AP) — U.S. home prices posted a robust gain in August — another sign that the American housing market remains strong despite economic fallout from the coronavirus pandemic.

The S&P CoreLogic Case-Shiller 20-city home price index, released Tuesday, showed that home prices climbed 5.2% in August from a year earlier, accelerating from a 4.1% gain in July. The gain was stronger than economists had expected.

Phoenix (up 9.9% from August 2019), Seattle (up 8.5%) and San Diego (7.6%) posted the biggest gains. All 19 cities in the index recorded price increases. The 20-city index excluded prices from the Detroit metropolitan area index because of delays related to pandemic at the recording office in Wayne County, which includes Detroit.

Helped by rock-bottom mortgage rates, the U.S. housing market has been a source of strength as the U.S. economy climbs back from an April-June freefall caused by the pandemic and the measures taken to contain it.

“The supply of for-sale homes, already extremely tight, has only become more constrained in recent months, and historically low mortgage rates continue to encourage many buyers to enter the market," Matthew Speakman, economist at the real estate firm Zillow, said in a research note. “This heightened competition for the few homes on the market has placed consistent, firm pressure on home prices for months now, and there are few signs that this will relent any time soon.''

The National Association of Realtors reported last week that sales of existing shot up 9.4% in September and that the median selling price of a home climbed 15% from a year earlier to $311,800. And the Commerce Department reported that home building rose 1.9% in September on a surge in construction of single-family homes.