The supply curve of labor becomes horizontal at that wage, up to the maximum quantity of labor that is willing to work at that wage. At the higher wage there will be a lower level of employment and some unemployment will be created. The union faces a conflict between the interests of employed and unemployed members. An alternative way to achieve higher wages is to restrict the supply of workers into the market. This may be achieved by increasing the length of apprenticeships, obtaining government certification or other regulations such as licensing.
Monopsony brings power to the demand side of the market.
As a single buyer of labor the monopsonist can offer any wage it chooses and workers must either accept it or find another job. The labor supply curve tells the monopsonist the wage is must offer to get a specific quantity of labor. A labor union in a monopsony market Suppose that workers in a monopsony labor market unioinize there is what is called bilateral monopoly monopoly on the demand side and on the supply side of the market. The wage will be determined in this situation through a process of collective bargaining the outcome of the process will depend on the objectives of the union and the relative bargaining strengths of the two sides. The union may also target a higher wage depending on how it trades off the wage and the level of employment.