Employees at South Korea's top 30 percent of companies in terms of sales are getting paid more than double the salaries of their counterparts in the bottom 30 percent, according to an analysis released on Thursday.

Data provided by a research team of local daily Energy Economic News said the average annual salary last year at the country's top 2,000 companies, sorted by their annual sales, was 47.3 million won ($39,983), an increase of 4.9 percent.  Petrochemical firms had the highest average of 85.4 million won, a 12 percent jump from the previous year.

The analysis covered both listed and unlisted firms.

Results showed that the pay at the top 30 percent averaged at 66.3 million won, compared to 28.3 million won for workers at the bottom 30 percent.

Fourteen of the companies had payrolls that exceeded 100 million won, 10 more than in 2014.  Data showed 29.9 percent of the companies had pay in the 40-million-won range, while 27.5 percent paid along a 30-million-won line.

To measure the salary gap between large conglomerates and small and medium-sized companies, the team compared firms with over 1 trillion won in sales with smaller enterprises with less than 100 billion won. Data showed those at big conglomerates were paid 67 million won, while workers at smaller companies received roughly 62 percent (42 million won) of it.

Such a gap is commonly blamed for a heavy preference for large business groups among job seekers, a point the team highlighted in its research. "It is the reality that the pay gap results from the difference in sales, profits and industry," O Il-sun, the team's chief, said. "But we would be able to ease the problem if workers at small firms got at least 70 percent of what people at the big firms get."

By industry, petrochemicals firms had the highest pay, led by SK Energy, with an annual average salary that rose to 101 million won last year from 88.5 million won in 2014.

Chemical firms came next at 53.3 million won. Construction companies followed with 53.2 million won.

Pay at food companies averaged 41.3 million won. For electronics firms, the average was 42.9 million won. The average for pharmaceutical companies was 44 million won, and 43.1 million won was for the logistics industry. (Yonhap)