South Korea's financial derivatives market suffered a sharp downfall in its trading volume last year on stricter regulations, data showed Monday. The turnover of financial derivatives on the local bourse reached 820 million contracts last year, down 55.3 percent from a year earlier, according to the data compiled by the Korea Exchange (KRX). In terms of amount, the turnover also sank 12.3 percent on-year last year, the data showed. The market slump came as the country's financial regulator imposed stricter rules for derivatives trading. From 2011, the regulator raised the minimum price to buy or sell options contracts in a bid to limit individual investors.