WASHINGTON (MarketWatch) - U.S. firms cut back their employees' working hours in the third quarter at the fastest rate in six years, keeping productivity growth rising more than expected, according to Labor Department data released Thursday. Productivity in the nonfarm business sector increased at a 1.1% annual rate as output fell 1.7% and hours worked dropped 2.7%. Economists surveyed by MarketWatch expected productivity to increase at a 0.3% annual rate. Unit labor costs - a key gauge of inflationary pressures from labor markets - rose 3.6% compared with the 4.2% expected by economists. Real hourly compensation fell 1.9% in the quarter and is down 0.9% in the past year, the largest annual decline in 13 years.