Construction demand continues on the incline, but the number of unemployed workers with construction experience has dropped drastically, according to analysis by the Associated General Contractors of America (AGC).

That total is the lowest for September since 2000. AGC officials caution that a hiring slowdown most likely reflects a lack of available workers and could lead to project delays unless more students and workers join the construction sector.

“Growth in the construction workforce has been slowing throughout 2015, just at the time that construction spending has accelerated to a multi-year high,” says Ken Simonson, AGC’s chief economist. “Contractors would love to hire more workers, but there aren’t enough qualified craft workers or supervisors available.”

Construction employment totaled 6,396,000 in September, the most since February 2009, but the total rose by only 8,000 in September and by 205,000 or 3.3 percent over the past year, Simonson says. In the previous 12 months, construction employment had risen by 298,000 or 5.1 percent.

The number of unemployed jobseekers in September who last worked in construction totaled 479,000, the lowest figure for the month since 2000. The unemployment rate for such workers was 5.5 percent, the lowest September number since 2001. Meanwhile, Census Bureau data released on October 1 showed that the growth in construction spending accelerated to a nine-year high of 13.7 from August 2014 to August 2015—up from a 2.7-percent rate a year earlier.