The market demand curve for labor shows the relationship between the wage and the quantity of labor employers wish to hire at any given wage, assuming all other things are held constant. The relationship between wages and the quantity of labor supplied by all workers in the market is depicted by the market supply curve of labor.

The market demand curve for labor is downward sloping because of diminishing value of the marginal product of labor (VMP_L) as more workers are hired. This means that as the market wage rate decreases, the value of the marginal product VMP_L of the last workers hired is now higher than the new wage rate. Employers are then willing to hire more workers at the lower wage rate.

Conversely, as wages rise, the value of the marginal product VMP_L of the last workers hired is now lower than the wage rate. This means that as the market wage rate increases, the value of the marginal product VMP_L of the last workers hired is now lower than the new wage rate. Employers are willing to employ fewer workers at the higher wage rate. .

The market supply curve for labor is upward sloping because higher wages attract more workers into the labor market. Each worker has a different minimum wage rate they require to get them to provide their labor in the workforce. As the prevailing market wage increases, this motivates more and more people to join the workforce.

The forces of demand and supply determine the equilibrium level of employment in the labor market. This equilibrium occurs at the point where the market demand curve for labor intersects the market supply curve for labor. At this point, the quantity of labor demanded by firms equals the quantity of labor supplied by workers. The wage rate that prevails under these conditions is the labor market equilibrium wage. In perfectly competitive input and output markets, all workers receive this wage and each employer firm is maximizing its profits.

At any wage rate higher than the market equilibrium wage, the quantity of labor workers are willing to supply exceeds the quantity of labor demanded by employers, resulting in a surplus of labor. In this scenario, unemployed workers are willing to accept lower wages to secure employment. This will bring the wages down, pushing the market back toward the equilibrium level of employment.

Conversely, at a wage rate below the equilibrium wage, the quantity of labor that is demanded by employers exceeds the quantity of labor available, leading to a labor shortage. To attract and hire the profit maximizing number of workers, employers are compelled to increase the wage they offer to workers. This will drive wages back up, pushing the market back toward the equilibrium level of employment.

These adjustments to market wages ensure that the labor market remains in balance, with wages adjusting to align the quantity of labor supplied and demanded.