Maine’s unemployment rate continued its historic run in September.

The state’s Department of Labor released a preliminary seasonally adjusted unemployment rate estimate of 2.9 percent for September on Friday. The rate is unchanged from August and down from 3.5 percent one year ago.

The September rate extends a streak of below 4 percent unemployment in the state to 45 consecutive months. The unprecedented streak – the longest since the state started keeping records – has contributed to a severe labor crunch for Maine employers, who cannot find enough people to fill existing openings. The crunch is further exacerbated by demographic trends that show more Mainers are retiring than entering the workforce, and more people are dying than being born.

It is especially severe in the Portland metro area, where September’s unemployment rate was estimated at 1.9 percent.

The number of unemployed Mainers is down 4,600 over the year to 19,700, according to the Department of Labor news release.

The private sector estimate of 531,800 jobs is up 3,100 over the year, with the largest job gains in the retail trade and manufacturing sectors. The government estimate of 100,300 jobs has not changed significantly in the last five years.

Maine’s unemployment rate is lower than the national average, which was 3.5 percent in September, down slightly from 3.7 percent for August and from 3.8 percent one year.

It’s also lower than the New England average, which is estimated at 3 percent. Rates for other states in the region are 2.5 percent in New Hampshire, 2.2 percent in Vermont, 2.9 percent in Massachusetts, 3.6 percent in Rhode Island and 3.6 percent in Connecticut.