NORTH BAY -- Unemployment rates across the North Bay (see chart) in March either remained at the previous month's high levels or inched upward, but Sonoma County continued a four-month stretch of substantial year-over-year job growth, reaching 5,000 net new jobs last month, according to state estimates released today.

Most counties saw slight increases in their jobless rates, including Sonoma County. The uptick in jobless claims is an indication that the labor force is growing, as previously unemployed workers reenter the job market, according to the state Employment Development Department.

Sonoma County

Sonoma County saw a slight increase in its March unemployment rate, to 10.4 percent from a revised 10.2 percent in February. Yet the 2.9 percent job growth over the previous 12 months is seen in the decline of the rate for the county from 11.2 percent in March 2010.

Napa County

In Napa County, the jobless rate remained unchanged at 10.3 percent from February to March. The rate a year ago was 10.6 percent.

The county had a net loss of 1,400 jobs, or 2.2 percent, over the previous 12 months.

Marin County

Marin County continued to post the lowest estimated unemployment rate in the state, at 8 percent, which was slightly up from last month's 7.8 percent. The year-ago rate in Marin was 9 percent.

Information on employment by industry in Marin isn't yet available.

Solano County

Solano County also saw a slight uptick, from 12.1 percent in February to 12.3 percent in March, which is just below last year's rate of 12.5 percent. The county had a net loss of 900 jobs, or 0.8 percent, from March 2010.

Mendocino County

Mendocino County's rate was 12.5 percent last month, up from February's 12.2 percent rate , but barely down the March 2010 rate of 12.4 percent.

The number of jobs in the county decreased 1.2 percent, or 340 positions, from 12 months before.

Lake County

The jobless rate for Lake County increased to 19.5 percent in March from 19.2 percent in February. The previous March, the rate was 19 percent.

The county had a 4.5 percent net loss in jobs, or 580, from the previous March.

Unemployment rates for North Bay countiesAreaMarch 2010

February 2011

March 2011State rank

(out of 58)Lake19.0%19.2%19.5%49Marin9.0%7.8%8.0%1Mendocino12.4%12.2%12.5%22Napa10.6%10.3%10.3%9Solano12.5%12.1%12.3%20Sonoma11.2%10.2%10.4%11California12.4%12.1%12.0%--U.S.9.1%8.9%8.8%--

Source: California Employment Development Department and the U.S. Bureau of Labor Statistics.