Japan's trade deficit more than quadrupled on year to US$3.7 billion (S$4.6 billion) in March, government data showed on Thursday, as a weaker yen inflated import costs. The monthly trade deficit expanded to 362.4 billion yen (S$4.6 billion) from the year-before shortfall of 81.8 billion yen, finance ministry data showed. The heavy deficit was still smaller than 480 billion yen economists predicted in a poll by the Nikkei business daily. Exports rose 1.1 percent to 6.27 trillion yen while imports climbed 5.5 percent to 6.63 trillion yen.