industrial action Certain sanctions available to groups of workers and employers in dispute with each other over employment conditions. A strike is a refusal by workers to continue working, usually involving a walk-out or concerted non-attendance at the workplace. Wildcat strikes are short and begin without notice. Unofficial strikes are called without formal approval from the workers' trade union. Sit-down strikes or sit-ins differ in that strikers remain on the employer's premises. Other sanctions available to workers and their trade unions include the work-to-rule, in which an officious and punctilious observation of factory or office rules is made to inconvenience management; go-slows in which work is carried out more slowly than normal; overtime bans in which workers refuse to work more than their standard hours; and blacking in which workers refuse to work with particular products or services. Aside from disciplinary action against individuals, the main equivalent sanction available to employers is the lock-out, in which the employer either dismisses workers or prevents them from entering the workplace. Measures of industrial action are often taken to be indicators of industrial conflict, though this is a broader and more difficult notion. Information on strikes and lock-outs, including numbers of disputes, numbers of working days lost, and numbers of workers involved, is available for many countries, though care is needed in analysis because of differing statistical definitions. Measures of other forms of industrial action are much less widely available.