Here are the key types of wage differentials:
1. Occupational/skill differentials: Wages vary based on the type of occupation, level of skill/experience required. Highly skilled jobs pay more.
2. Industrial differentials: Wages differ across industries based on supply/demand of labor, capital intensity, unionization etc. Mining pays more than retail.
3. Area/geographical differentials: Cost of living varies in different areas so wages are higher in urban/expensive areas compared to rural areas.
4. Interplant/intra-plant differentials: Wages may differ between plants of the same company or within departments of a plant based on profitability, technology used etc.