Major South Korean conglomerates saw their profitability deteriorate in 2012 from four years earlier due to the global economic slowdown and weak domestic demand, data showed Sunday. The top 20 family-controlled conglomerates, known here as chaebol, posted an average operating profit margin of 5.6 percent last year, compared with 6.3 percent in 2008, according to the data by the Korea Exchange and Chaebul.com, which tracks the country's conglomerates.