The number of people who could afford to purchase median-priced homes in the Los Angeles region fell sharply in December from the year-earlier period but gained one percentage point from November, the California Association of Realtors said.

The monthly California Housing Affordability Index, a measure of home affordability based on home prices, income and mortgage rates and other housing costs, showed that 12 percent of Los Angeles households could afford to purchase a median-priced home in December, down from 17 percent a year earlier but up from November’s 11 percent.

The index is largely dependent on median home prices, which rose to $552,760 in December from $463,450 one year earlier but slipped from November’s $575,310, according to the CAR.

Statewide, 14 percent of the population could afford to buy a home, down from 19 percent in the year-ago period but unchanged from November. The median home price statewide in December was $548,430, versus $474,270 a year earlier and down from $548,680 in November.

The areas with the highest levels of affordability were the High Desert region, which includes Palmdale and Lancaster, with 24 percent of households qualifying, and San Bernardino County, at 20 percent. The least affordable markets were Santa Barbara County, where only 6 percent of households could afford to buy a median-priced home, and Sonoma County and the Northern Wine Country region, both remaining at 7 percent from the month before.

Santa Barbara County’s South Coast area had the most expensive homes, where the median price was about $1.3 million in December. Homes in the High Desert region were the most affordable, at $320,490.