U.S. worker productivity increased at its fastest pace in three years in the third quarter, holding down labor costs, but the trend in productivity growth remained moderate. The Labor Department said on Thursday that nonfarm productivity, which measures hourly output per worker, rose at a 3.0 percent annualized rate. That was the quickest pace since the third quarter of 2014. Growth in second-quarter productivity was unrevised at a 1.5 percent rate. Economists polled by Reuters had forecast productivity rising at a 2.4 percent pace in the July-September quarter.