The Labor Department revised the figure upward from a 1.7% gain reported in January.The upward change stems from a revision in output, the agency said. Initial figures said that fourth-quarter output rose 3.9% from the preceding quarter. The revised figures showed that output actually increased 5.2% from the previous quarter. The revised figures for the year also showed that unit labor costs rose 1.4% in 1984, the same rate of increase recorded in 1983.