Final answer:
The marginal product of labor typically decreases after hiring additional workers due to the principle of diminishing marginal productivity, which occurs when additional labor becomes less efficient because other factors of production remain fixed.
Step-by-step explanation:
When a unit of labor is hired, the marginal product of labor typically declines as the employer hires additional workers. This phenomenon occurs due to diminishing marginal productivity, which happens because in the short run, the capital and other factors of production are fixed, and only labor is variable. Initially, new workers may contribute significantly to production, but as more workers are added, they become less effective because the fixed capital becomes a limiting factor.
For example, after hiring a second worker, that person might alleviate a major bottleneck in the production process. A third worker could perform supporting tasks, but their contribution to productivity might be less than the second worker's due to limited equipment or space.