Unemployment fell to 5.7 percent in Sonoma County in December, down from a revised 6.0 percent in November 2013 and below the year-ago estimate of 7.8 percent, the state reported Friday.

The jobless rate has now declined in four of the last five months, reaching levels not seen since the summer of 2008. The drop, however, is not the result of an increase in hiring by local companies, the state Employment Development Department reported.

While the local economy is stronger than it was a year ago, employment declined in December for the second straight month. There were 183,000 wage and salary jobs in Sonoma County in December, a loss of 1,000 jobs from November. A year ago, there were 178,300 jobs in the county.

The jobless rate had fallen this winter in tandem with a contraction in the county's labor force and a reduction in the number of unemployed job seekers, according to EDD data. There were 14,600 unemployed workers in Sonoma County in December, down from 15,600 in November and 20,100 a year ago.

Statewide, unemployment dropped to 8.3 percent in December, down from 9.8 percent a year ago. The U.S. unemployment rate was 6.7 percent in December.

The state Employment Development Department reported Friday that California added 13,600 nonfarm payroll jobs during the month, bringing total job gains in the state to 922,500 since February 2010, when the recovery from the recession began.

Despite adding 235,700 jobs in 2013, higher-wage sectors such as manufacturing and construction posted declines in December. Manufacturing saw the biggest drop, with 6,000 job losses.

Marin, San Francisco and San Mateo counties had the lowest unemployment rates, all below 5 percent.

Colusa and Imperial counties had the highest, above 20 percent.

The Associated Press contributed to this story.