Labor Market Imperfections

Insufficient/misleading job information Change in Inputs This prevents workers from seeking better employment.
Geographical Immobility Many people are reluctant or too poor to move so they accept a lower wage
Unions - Collective bargaining and threats to strike often lead to higher than equilibrium wages.
Wage Discrimination - Some people get paid differently for doing the same job based on race or gender. (Very illegal!)
An imperfectly competitive labor market is called a Monopsony.