Disputes involving the labour force that result in collective work stoppages are a grievous source of economic loss that can occasion irreparable harm. One form of collective work stoppage is strikes. They usually take the form of employer-employee or management-labour conflict. In this context, there are different methods: a sympathy or solidarity strike to support another branch of workers who are striking; a slowdown or work-to-rule (which results in slowdown) strike, which allows work to continue but at a reduced pace; a wildcat strike, called by local union branches but not endorsed officially by the union as a whole (and generally disapproved of by union headquarters); a work stoppage, when workers cease work but do not leave the place of work; and a rotating or checkerboard strike, affecting first one area of production then another so that the work schedule is disrupted.
There are other interests that can diverge enough to cause a strike. Organized labour can be its own adversary in territorial battles between rival unions, and strike actions may be initiated to force or to prevent elections by the work force as to which union they wish to represent them. Local or national government may intervene in industrial affairs by embargoes, general labour legislation, industry regulation, expropriation, subsidy, nationalization, and emergency powers. In socialist countries labour disputes can only be with the government.
Strikes may be illegal, as breaches of contract with employers, or in violation of public laws or governmental restrictions. Similarly employer action (whether private or public ownership) can illegally employ 'strikebreakers' and 'scabs' to physically intimidate or replace striking workers by non-union workers.
Strikes inevitably involve government, possibly commencing with governmental arbitration or proceeding to the courts of justice. In a general strike, the striking workers, and the political parties and individuals supporting them, may come into violent conflict with the police or military forces of a country. There have been a substantial number of deaths caused by strikes, particularly general strikes, and labour issues are perhaps the single most polarizing factor in the developed countries.
At the beginning of the 20th century, one third of all strikes in the USA were by unorganized employees. The proportion decreased and now, since 1933, strikes are uniformly confined to unionized workers.
In 1986 the International Labour Organization says that 65.3 million working days were lost through strikes in 52 countries. There were 14,200 strikes in 1986 down from 15,500 during the previous year. The size of the strikes increased from an average from 810 workers in 1985 to 827 workers and lasted an average of 5.5 days an increase of one half day. Increasing automation has, however, reduced the effectiveness of strike actions. A 1959 strike by workers in the American oil industry failed because a relatively high rate of production was maintained by the automated system alone. Similarly a 1983 strike by communications workers failed because of the computerized telephone exchange systems.
Economic decline has also been a limiting factor. In the USA auto industry, a strike failed because manufacturers were content to use up a large inventory before bargaining to resume production. Foreign competition has often encouraged employees and employers to agree on no-strike provisions to ensure stability of domestic production, such as in the steel industry in 1982. Increasingly, too, public opinion does not oppose the hiring of unemployed persons to replace strikers, particularly when the latter have used violent techniques. An example of this is the air traffic controllers strike in the US in 1982, when public opinion was against the strikers.