The most reliable and effective protection for most workers is provided by the existence of many employers. As we have seen, a person who has only one possible employer has little or no protection. The employers who protect a worker are those who would like to hire him. Their demand for his services makes it in the self-interest of his own employer to pay him the full value of his work. If his own employer doesn’t, someone else may be ready to do so. Competition for his services—that is the worker’s real protection.

– Milton Friedman, Free to Choose