Wage differentials exist between workers due to differences in ability, effort, occupation, and locality. Wages are usually higher in some localities than others primarily because of differences in cost of living. However, people are often reluctant to relocate for higher wages due to non-monetary costs like leaving friends and family, selling a home, changing schools for children, losing seniority or benefits. Occupational licensing requirements can also prevent workers from moving to a new area for higher pay if they need a new state license.