The turnover ratio of corporate bonds in South Korea fell to the lowest mark in five years, mainly due to a lack of demand stemming from lower yields and the bankruptcy of two major conglomerates, data showed Monday. The turnover ratio of corporate bonds sold in the over-the-counter (OTC) market here stood at 4.83 percent this month, the lowest since the 3.36 percent tallied in the same month of 2008, according to the data by the Financial Supervisory Service (FSS) and the Korea Financial Investment Association (KFIA)