The Shanghai Gold Exchange (SGE) will cut silver margin requirements back to 18 percent from 19 percent from May 13 settlements if there is no sharp movement in prices, it said on Friday. The SGE has hiked margin requirements for its silver forward contract five times since April 25 in order to curb volatility in the market. The surge in speculative silver trade in Shanghai is being blamed for the rapid rise and subsequent crash in silver prices over the year.