NEW YORK — 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. High rates were also seen in carpenters, miners, electricians and people who work in construction.