1. What causes shifts of labor supply?

2. Changes in preferences and social norms
Changes in population
US labor force grows approximately 1% a year
Policies affecting immigration affect population growth, and thus labor force
Changes in preferences and social norms
For example, more women working

3. Changes in opportunities
Offshoring has diminished some manufacturing jobs
Less job discrimination for women in professions such as medicine, law, engineering
High wages in one market may attract workers away from another market.
Changes in wealth
Early retirees from tech boom may value leisure more than work
Stock market declines may cause many new retirees to reenter work force