South Korea\'s major listed firms performed worse in the fourth quarter of 2011 than three months earlier largely due to a global economic slowdown and the eurozone debt turmoil, data showed Wednesday. The combined operating profit of 108 listed companies is estimated at 27.4 trillion won (US$23.8 billion) for the October-December period, down 5.49 percent from the previous quarter, according to the data by local financial information provider FnGuide.