The combined debt of South Korea's 30 major conglomerates by assets nearly doubled to about 600 trillion won (US$558 billion) in five years as they expanded their businesses, data showed Tuesday. About half of family-controlled conglomerates, known as chaebol, saw their debt ratio also increase, according to the data compiled by Chaebul.com, which tracks the country's conglomerates. The total debt of the 30 conglomerates amounted to 574.9 trillion won at the end of last year, up 83% from 261.1 trillion won in 2007, Chaebul.com said, according to (Yonhap) news agency. In comparison, the country's national debt stood at 443.1 trillion won last year. It is projected to expand to 480.3 trillion won this year and 515.2 trillion won next year. The website said chaebol's debt ratio fell to 88.7% in 2012 from 95.3% in 2007. Still, the average debt ratio of 28 other conglomerates, excluding Samsung Group and Hyundai Motor Group, edged up to 115.4% in 2012 from 113.7% in 2007. The data findings indicate that financial health of 28 chaebol worsened in five years. One of the 28 conglomerates is Tong Yang Group, whose debt ratio jumped to 1,231% in 2012, from 146% in 2007. Jeong Sun-sup, the head of Chaebul.com, warned that the growing debt could cause trouble for the country's economy unless the debt is properly managed.