Labor spying in the United States had involved people recruited or employed for the purpose of gathering intelligence, committing sabotage, sowing dissent, or engaging in other similar activities, in the context of an employer/labor organization relationship. Spying by companies on union activities has been illegal in the United States since the National Labor Relations Act of 1935. However, non-union monitoring of employee activities while at work is perfectly legal and, according to the American Management Association, nearly 80% of major US companies actively monitor their employees.