The unemployment rate for the construction industry fell to 8.5 percent in September, the lowest rate in September since 2007, though just 20,000 jobs were added to the 5.8 million-strong workforce. Recent declines in the unemployment rate can be attributed to workers leaving the industry, which could lead to a shortage of skilled labor as new construction ramps up.

Construction employment rose by 20,000 in September, and the industry's unemployment rate fell to a six-year low of 8.5 percent, according to an analysis of new government data by the Associated General Contractors of America.

''Both of these reports show the industry was doing relatively well before the federal government shutdown forced many firms to hit the pause button,'' said Ken Simonson, the AGC's chief economist. ''But the shutdown likely disrupted a wide variety of projects and may have caused private investors and developers to delay decisions about new projects or plant expansions. As a result, future spending and hiring gains may be weaker.''

Construction employment totaled 5,826,000 in September, a gain of 20,000 from the August tally, which was revised up from the Labor Department's initial estimate by 8,000.

The September figure is 3.4 percent higher than in September 2012, while aggregate weekly hours of all construction employees rose 4.2 percent over the year, indicating that companies are adding to existing workers' hours in addition to hiring new employees. Employment climbed for the month and year in both residential and nonresidential construction.

The industry's unemployment rate dropped sharply over the past year, from 11.9 percent in September 2012 to 8.5 percent in September 2013"?uthe lowest September rate since 2007. The steep decline in the number of unemployed former construction workers suggests companies may have trouble finding experienced workers if the volume of projects continues to expand.