South Korean lenders saw their profit sink more than 50 percent last year as they suffered a decline in interest income and set aside more reserves against bad loans, the financial regulator said Thursday. The combined net income of 18 local banks, including market leaders Woori and Kookmin, reached 4 trillion won (US$3.77 billion) in 2013, down from the 8.7 trillion won the previous year, according to the Financial Supervisory Service (FSS).