Since early 2020, the S&P CoreLogic Case-Shiller U.S. National Home Price NSA Index annual gains have always increased each month -- until now. The S&P reported a 19.8% annual gain in August, which is the same as the previous month.

Analysts believe it is a sign that the housing market could be stabilizing.

“We have previously suggested that the strength in the U.S. housing market is being driven, in part, by a reaction to the Covid pandemic, as potential buyers move from urban apartments to suburban homes. August data also suggest that the growth in housing prices, while still very strong, may be beginning to decelerate,” Craig Lazzara, managing director and global head of index investment strategy at S&P DJI, told CNBC.

The 10-City Composite annual increase was 18.6%, down from 19.2% in the previous month, while the 20-City Composite showed a 19.7% year-over-year gain, down from 20% in the previous month. Consensus estimates called for a 20% increase, according to Barons.

Eight of the 20 cities reported a higher increase in prices in the year as of August 2021 compared to July 2021. Phoenix led with a 33.3% year-over-year price increase, followed by San Diego at 26.6% and Tampa at 25.9%.