Worker's compensation, provision by employers of medical, cash, and sometimes rehabilitation benefits for workers who are injured in accidents at work. In the United States all states (Wisconsin was the first) have had worker's compensation laws since 1949, but 20% of all workers are unprotected. Railroad employees and merchant seamen are covered by other legislation. Before the first effective U.S. compensation acts, passed in 1908–11, injured employees were dependent on their employers' financial goodwill or on winning a negligence suit against them. Present laws are based on the principle of “liability without fault,” which assumes that accidents are inevitable and that their costs are a legitimate business expense.