A jolting tumble in South Korean stocks in the first two trading days of the year has wiped out nearly 1.1 trillion won (US$1 billion) in the value of stocks owned by chiefs of top 10 business groups, industry data showed Sunday. According to the data compiled by Chaebul.com, a conglomerate research firm, the combined value of stocks held by the top 10 chiefs, including Lee Kun-hee of Samsung Group, reached 26.29 trillion won at the market closing on Jan. 3, down 4.2 percent from 27.44 trillion won on Dec. 30, the last session of 2013.