Farmers, lumberjacks and fishermen have the highest suicide rate in the U.S., while librarians and educators have the lowest, according to a large study that found enormous differences across occupations.

The study didn’t explore the reasons behind the differences, but researchers found the highest suicide rates in manual laborers who work in isolation and face unsteady employment.

Thursday’s report from the Centers for Disease Control and Prevention is perhaps the largest U.S. study to compare suicide rates among occupations. But it is not comprehensive. It only covers 17 states, looking at about 12,300 of the more than 40,000 suicide deaths reported in the entire nation in 2012. Because of the limited data, they could only calculate suicide rates for broad occupation categories, but not for specific jobs. The categories, which sometimes seem to group professions that have little to do with each other, like athletes and artists, are based on federal classifications used for collecting jobs-related data. Suicide is the nation’s 10th leading cause of death. Public attention often focuses on teens and college students, but the highest numbers and rates are in middle-aged adults. Suicide is far more common in males, and the rankings largely reflect the male suicide rates for each group.

CDC’s occupational suicide list:

1. Farmworkers, fishermen, lumberjacks, others in forestry or agriculture; 85 per

100,000

2. Carpenters, miners, electricians,

construction trades; 53

3. Mechanics and those who do installation, maintenance, repair; 48

4. Factory and production wokers; 35

5. Architects, engineers; 32

6. Police, firefighters, corrections workers, others in protective services; 31

7. Artists, designers, entertainers, athletes, media; 24

8. Computer programmers, mathematicians, statisticians; 23

9. Transportation workers; 22

10. Corporate executives and managers, advertising and public relations; 20

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