1. The wage fund theory advocated by John Stuart Mill assumes that the supply of labor is fixed and demand for labor consists of a fixed sum determined by capitalist employers, with demand determined by the size of the wage fund. 2. The standard of living theory advocated by Karl Marx assumes that wages should allow workers to support themselves and their families and live comfortably according to societal standards. 3. The bargaining theory proposed by John Davidson assumes that wages are determined by the relative bargaining power of employers and employees.