The Japanese economy grew at an annual rate of 3.9 per cent in the January-March period, revised up from an initial estimate of 2.4 per cent, due to strong corporate investment, the government said Monday, according to dpa. The reading was better than the 2.7-per-cent growth forecast in a poll of economists by the Nikkei business daily. The growth in corporate investment jumped 2.7 per cent quarter-on-quarter, revised up from an initial figure of 0.4 per cent, the office said.