SEOUL, April 28 (Yonhap) — Operating margins of South Korea’s top 100 companies fell to a six-year low in 2019 amid high labor costs, data showed Tuesday.

Their average operating margin of the leading firms by sales stood at 4.5 percent last year, the lowest level since 2013, according to market research service provider CXO Institute.

The figure refers to the ratio of operating income to sales and serves as a key barometer of a company’s profitability.

Their combined sales slowed to 964 trillion won (US$788 billion) in 2019 from 100.6 trillion won the prior year with their total operating income tumbling to 43.6 trillion won from 97.6 trillion won.

The corporations’ combined operating income was also the lowest since 2013 due mainly to sluggish sales. High personnel expenses were partly responsible.

The firms’ total labor costs reached 68.2 trillion won last year, with their ratio to turnover coming to a six-year high of 7.1 percent.

Last year, the average annual salary for employees at 20 of the top 100 companies came to 90 million won or higher, up from five six years earlier.

The number of firms with a per-capita salary of 100 million won or larger rose to 10 from two over the cited period, according to the data.