WASHINGTON (AP) — U.S. productivity posted a sharp rebound in the January-March quarter after having fallen in the previous quarter. Labor costs declined slightly. The Labor Department reported Thursday that productivity increased at an annual rate of 5.4% in the first quarter, recovering from a 3.8% rate of decline in the fourth quarter of last year. Labor costs fell at a 0.3% rate in the first quarter following a 5.6% jump in the fourth quarter. It was the biggest quarterly rise in productivity since an 11.2% surge in the second quarter of last year, a gain that reflected the fact that output was not falling as fast as the labor market was shrinking as millions of people were being laid off after the pandemic hit.