Locally and nationally, businesses are hiring more contract labor as they adjust their workforces to keep pace with a still-uncertain economy, a trend that has long been a precursor to more widespread employment growth.

At Professional Staffing Group in Boston, the number of workers on assignments is up 50 percent over the past eight months, said company President Aaron Green. “Over the past couple months, we have started to see the demand spreading to smaller-sized companies,” he said. “But I still wouldn’t call the market robust.”