The 3 stages of production are characterized by the slope and form of the overall product curve. the primary stage is characterized by AN progressively positive slope, the second stage by a decreasingly positive slope, and also the third stage by a negative slope. as a result of the slope of the overall product curve IS marginal product, these 3 stages also are seen with marginal product. In Stage I, marginal product is positive and increasing. In Stage II, marginal product is positive, however decreasing. And in Stage III, marginal product is negative.