Orange County’s unadjusted jobless rate dipped to 2.4% in December, down slightly from a revised 2.5% the month before and below the year-ago estimate of 2.7%, according to the state Employment Development Department.

OC’s lowest-ever rate was 2.2% in December 1999.

California’s rate was 3.7% and the U.S.’s was 3.4% last month. The most recent December numbers for the county, state and U.S. aren’t seasonally adjusted.

OC non-farm employment increased by 6,200 jobs to just over 1.69 million in December from November. Six of the 11 employment sectors declined, while five increased.

Professional and business services reported the largest increase, adding 4,900 jobs, while retail trade grew by 900 positions.

The largest employment loss was in government, down by 1,000 jobs, all of it in local government, while construction was down by 200 last month.