The official Purchasing Managers’ Index (PMI), published by the National Bureau of Statistics, dipped to 51.0 in December from 51.4 the month before, signifying weakened export orders and output, Reuters reported.The 50-point mark on the index separates an expansion in activity from a contraction. Many economists have said China’s economy was likely to show weaker momentum in the final three months of 2013 after a rebound between July and September. “Both domestic and overseas demand was weaker than expected. Domestically, tight liquidity is weighing on factory output and orders,” said Li Heng, an economist at Minsheng Securities in Beijing.