Young South Koreans generally tend to be less happy the longer they work, a report published by a state-run organization showed Monday.

The amount of labor that employees aged 34 or younger are most satisfied with is between 15 and 40 hours a week, according to the report published in the journal of the Korea Labor Institute.

Researcher Park Ju-sang, of the Korea Labour & Society Institute took the data from the Korean Employment Information Service and categorized South Korean employees aged 34 or younger, based on how much time they worked in a week: under 15 hours, 15-40 hours, 41-52 hours, and over 52 hours.

He found that 59.4 percent of those working 15-40 hours a week answered that they are satisfied with their life, while 50.4 percent of those working 41-52 hours, and 45.4 percent who worked over 52 hours said so.

But the satisfaction rate of the group that worked the least, less than 15 hours a week, was 52.3 percent, showing that working less does not always mean a happier life.

The number dissatisfied with life, however, went up with work hours. The percentage of people who said they were not satisfied with life was 7.4 percent for the two groups with the shortest working hours, followed by 13.9 percent for those working 41-52 hours a week, and 17 percent for those working longer.

"After controlling factors such as school, job, and other socio-demographic factors, we found consistent evidence that the work hours affect an employee's happiness. ... We also found that happiness particularly tended to decrease with longer working hours among people with regular jobs," Park said.

Other factors that affected happiness were marriage, education, and the wealth of their parents. People who were married, or who graduated from Seoul area universities, and people with wealthier parents tended to be happier. But in the case of jobs, people working in the greater Seoul region tended to be less happy than those who worked elsewhere, the study showed.