When workers have a union, the supply of labour is said to be

When workers have a union, the supply of labour is said to be monopsonistic. A monopsony occurs when there is only one buyer of a particular good or service. In the case of labor, a monopsony occurs when there is only one employer in a given market or industry. A union represents workers in their negotiations with their employer, and can act as a kind of monopoly on the supply of labor in that market. Because the union negotiates on behalf of all the workers in the industry, the employer must deal with the union if they want to hire any of those workers. This can give the union significant bargaining power and allow it to negotiate better wages, benefits, and working conditions for its members. As a result, the supply of labor becomes monopsonistic because the employer must deal with the union, which represents the entire pool of available labor in that market.