U.S. employers added just 88,000 jobs in March, the fewest in nine months and a sharp retreat after a period of strong hiring. The slowdown may signal that the economy is heading into a weak spring. The Labor Department said Friday that the unemployment rate dipped to 7.6 percent, the lowest in four years, from 7.7 percent. But the rate fell only because more people stopped looking for work. People who are out of work are no longer counted as unemployed once they stop looking for a job.