Volume in the world's most actively traded derivative could fall following regulatory action. Sparked by rising credit card delinquencies that hampered economic growth last year, Korea's markets regulator, Financial Supervisory Service (FSS) is moving to curb retail speculation on the Kospi options and futures contracts, fearing that large aggregate losses could lead to slower consumer spending.

The Kospi 200 option is the world's most heavily traded contract with average daily volume of 10m lots...