Police unions in the United States include a large number and patchwork variety of organizations. Of those unions which conduct labor negotiations on behalf of its police members, 80% are independent and have no affiliation to any larger organized labor groups. There were a reported 800,000 sworn officers in the United States as of 2017, and an estimated 75-80% of them belonged to a union. Many of the independent unions serve police in local municipalities. The self-described "largest municipal police union in the world" is the Police Benevolent Association of the City of New York that represents 24,000 members of the NYPD. There is no single dominant national association. Four associations have significant membership drawn from across the country. The Fraternal Order of Police has a reported 330,000 members, although the FOP encompasses both union lodges and fraternal lodges, and while active as an advocacy group is not itself officially a union. The largest national union per se is the International Union of Police Associations, with about 20,000 members, which is among that 20% of police unions with affiliations to organized labor. The IUPA chartered with the AFL–CIO in 1979. Likewise the International Brotherhood of Police Officers has a national scope, and is a member organization of the National Association of Government Employees, which is itself affiliated with the Service Employees International Union. The history of police labor organization in the U.S., under the hand of Samuel Gompers and the American Federation of Labor, began in June 1919. Within four months an ill-advised strike by the freshly chartered Boston Police Department resulted in four days of public disorder, nine deaths, and widespread property damage. Woodrow Wilson declared that the strike was a "crime against civilization", and Herbert Hoover telegrammed Gompers, "There is no right to strike against the public safety by anybody, anywhere, any time." For decades afterward, police and other public employees were prevented from organizing. Only in the 1960s did most state laws change to allow public-sector employees the right to collective bargaining. In recent times police unions have been characterized as impediments to organizational reform, and as hindrances in attempts to discipline police officers involved in misconduct. Unions frequently oppose criminal justice reform proposals, as well as have promoted rioting and strikes when governments introduce organizational reforms. Structure Police are still highly unionized in the United States in the 21st century, in contrast to the declining union