South Korea issued a record amount of 50,000 won banknotes -- the country’s highest denomination bills -- in 2015, according to data from the central bank. 

Last year, the Bank of Korea issued some 20.5 trillion won ($16.99 billion) worth of 50,000-won notes, up 34.8 percent from the previous year, breaching the 20-trillion-won mark for the first time since it introduced the bill in 2009.

The increase was partly due to a rise in demand, the bank said. But the bills also had an unusually low rate of return that possibly indicates a flow of large sums into the so-called underground economy.

The underground economy refers to undetected and unregulated business activities that includes slush funds.

The return rate of 50,000-won bills stood at 40.1 percent last year, compared with 25.8 percent from the previous year, according to the BOK. The rate is, however, still lower than those of lower denomination bills at well over 80 percent.

The central bank said it also issued 14.38 trillion won worth of 10,000-won bills in 2015, down 12.3 percent from a year earlier while the amount of 5,000-won bills issued also dropped 5.9 percent on-year to 412 billion won over the cited period.

(khnews@heraldcorp.com)