Thirty-nine states have added construction jobs in the past year, but a growing number of contractors are having trouble finding workers, which could jeopardize future growth.

The statistics and opinion come from an analysis of Labor Department data from the Associated General Contractors of America. AGC said that while employment grew between July 2015 and July 2016, only 23 states and Washington, D.C., have added jobs in the last two months.

Many states are now experiencing construction employment declines as workers are hard to find, said StephenE. Sandherr, chief executive officer for the association.

"Depending on market segment and geography, many firms report they are having a hard time finding enough workers to keep pace with demand," Sandherr said.  "While there is slack in key segments like infrastructure and parts of the country that are struggling economically, many of these declines likely have more to do with firms not being able to find workers than not being able to find work."