The Bank of Japan has introduced a negative interest rate in a surprise move. The benchmark rate of -0.1% means that the central bank will charge commercial banks 0.1% on some of their deposits. It's hoped the moves will encourage banks to lend, and counter the ongoing economic slump in the world's third-largest economy. Investors cheered the surprise stimulus as Japan's share prices rose 476.85 points to close at 17,518.30 points at the Tokyo Stock Exchange, after the plans were unveiled.