Microeconomics · Unit 5: Factor Markets · 14 min read · Updated 2026-05-11
Factor Demand — AP Microeconomics
AP Microeconomics · Unit 5: Factor Markets · 14 min read
1. What Is Factor Demand?★★☆☆☆⏱ 3 min
Factor demand is the demand by profit-maximizing firms for any factor of production (labor, capital, land, or raw materials) to use in producing goods and services. Unlike demand for final goods and services (direct demand based on consumer utility), factor demand is always a **derived demand**—it depends entirely on consumer demand for the final output the factor produces.
Per the official AP Microeconomics CED, factor demand is a core component of Unit 5, making up roughly 10-15% of the unit's exam weight, translating to 2-3 multiple-choice questions per exam, and often a portion of a free-response question.
2. MRP and the Profit-Maximizing Hiring Rule★★★☆☆⏱ 4 min
The entire logic of factor demand derives directly from the firm's core goal of profit maximization. A firm will hire an additional unit of a factor if and only if the additional revenue it gains from that unit is greater than the additional cost of hiring the unit.
The profit-maximizing hiring rule states that a firm hires up to the point where $MRP = MFC$ (marginal factor cost). For perfectly competitive factor markets, $MFC$ equals the market factor price (e.g. $MFC = w$ for labor), so the rule simplifies to:
MRP = w
3. The Factor Demand Curve★★★☆☆⏱ 3 min
The individual firm's factor demand curve is identical to its marginal revenue product (MRP) curve. By definition, the demand curve plots the profit-maximizing quantity of the factor at every possible factor price. Since the profit-maximizing quantity always satisfies $MRP = w$, the MRP curve traces out all profit-maximizing (quantity, factor price) pairs.
Because of the law of diminishing marginal returns, the MRP curve is always downward-sloping: as the firm hires more of a factor, holding other inputs constant, the marginal product of the factor falls, so MRP falls at higher quantities.
Product market structure affects the position of the factor demand curve: a monopolist in the output market has $MR < P$, so MRP is lower at every quantity than a competitive firm with the same MP schedule. This means the monopolist's factor demand curve is to the left of the competitive firm's, so the monopolist hires less labor at the same wage.
4. Shifters of Factor Demand★★★☆☆⏱ 4 min
Any change that alters the marginal revenue product of a factor at every quantity will shift the entire factor demand curve. A change in the factor price itself only causes a movement along the existing factor demand curve, because the factor price is the variable on the vertical axis.
**Change in demand for the final product**: Increase in final demand raises MRP, shifting factor demand right; fall in final demand shifts left.
**Change in the price of other factors**: If substitute price falls, original factor demand shifts left; if complement price falls, original factor demand shifts right.
**Change in productivity**: Higher productivity raises MP, increasing MRP and shifting demand right; lower productivity shifts left.
**Change in number of firms**: More firms increase market factor demand, shifting the curve right; fewer firms shift left.
Common Pitfalls
Why: Students mix up quantity demanded vs demand, forgetting the wage is on the vertical axis.
Why: Students learn VMP from perfect competition examples and incorrectly apply it to firms with market power.
Why: Students default to the substitute case and forget that capital and labor can be complements.
Why: Students confuse total profit calculations with marginal profit maximization.
Why: Students confuse demand and supply sides of the factor market.