The number of people who could afford to purchase median-priced homes in the Los Angeles region dropped sharply in October from the year-earlier period and fell one percentage point from September, 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 October, down from 17 percent a year earlier.

The index is largely dependent on median home prices, which dropped to $557,730 in October from $458,210 one year earlier, according to the CAR. In September, the median home price in L.A. County was $560,990.

Statewide, 15 percent of the population could afford to buy a home, down from 19 percent in the year-ago period and unchanged from September. The median home price statewide in October was $538,770, versus $459,530 a year earlier and down from $543,980 in September.

The areas with the highest levels of affordability were the High Desert region, which includes Palmdale and Lancaster, with 25 percent of households qualifying, and San Bernardino County, at 22 percent. The least affordable markets were the Northern Wine Country region and Sonoma County, where only 7 percent of households could afford to buy a median-priced home. Santa Barbara County’s South Coast area had the most expensive homes, where the median price was nearly $1.2 million in October.

Nationwide, the median home price was $218,000 in October, up $6,000 from a month earlier.