South Korea''s listed companies saw their earnings drop 5% on-year in the first half of the year amid unstable external economic conditions, a report showed Wednesday. The combined net profit of 469 of 660 companies, which are listed on the main bourse and close their books on December 31, reached 4.19 trillion won (US$3.9 billion) in the January-June period, compared with 4.41 trillion won a year earlier, according to the report by the Korea Exchange and the Korea Listed Companies Association. Numbers for the remaining companies are not available, it said. The report showed the firms'' total revenue increased 11.9% on-year to 100.39 trillion won in the six-month period, while operating profit slipped 2.2% to 5.81 trillion won. The weaker bottom line came as firms'' profitability slipped on a rise in oil and raw material prices amid worsening external economic uncertainties, according to South Korea''s (Yonhap) news agency. "Revenue climbed on robust shipments of cars and steel products as well as big orders on overseas construction projects," the report said. Earnings and operating profit, however, slipped due to difficult external conditions stemming from the eurozone''s debt crisis, the slowing US economy and decreased consumption following Japan''s earthquake, it said. Around 81% of the tallied companies earned money in the first half, while the remainder suffered net losses, the report said. The average debt ratio of the tallied firms came in at 85.28% as of end-June, up 2.01 percentage points from the end of 2010, according to the report.