Unit 5: Factor Markets

What Factor Markets Are (and Why Their Demand Is “Derived”)

A factor market (also called a resource market or input market) is where households sell productive resources and firms buy them. You can think of factor markets as the place where companies buy what they need to produce goods and services. The key factors of production emphasized in AP Micro are labor (workers’ time and skills), land (natural resources and locations), and capital (machines, tools, buildings—physical capital).

The most important idea in Unit 5 is that firms don’t want inputs “for their own sake.” Firms demand inputs because inputs help them produce output they can sell in the product market. That makes factor demand a derived demand: the demand for a resource is derived from (depends on) the demand for the final product.

Product markets vs. factor markets

In a product market, a firm is a seller and consumers are buyers. In a factor market, the roles flip: households are sellers (of labor, land, etc.) and firms are buyers.

A helpful way to keep this straight is to focus on what the “price” represents:

• In a product market, price is what consumers pay per unit of output.
• In a labor market, the “price” is the wage rate—what firms pay per unit of labor (often per hour).
• In a land market, the “price” is rent.
• In a capital market (for physical capital services), the “price” is the rental rate.

Why derived demand matters

Derived demand means anything that increases the value of what the input produces will tend to increase demand for the input. For example:

• If consumers suddenly want more coffee, coffee shops want more baristas.
• If the price of an app rises (or the app sells more), the firm will likely hire more software engineers.

It also means input demand is not only about wages or rents—it depends on productivity and on product-market conditions.

Core vocabulary you must recognize

You’ll see these terms repeatedly in questions about factor markets:

• Marginal revenue product (MRP): the additional revenue generated by an additional resource/worker.
• Marginal factor cost (MFC): the additional cost of an additional resource/worker.

(You’ll also see marginal resource cost (MRC) used; in many AP-style setups, it’s used interchangeably with the cost of hiring one more unit of the input. In a competitive labor market for a wage-taking firm, that marginal cost is the wage.)

Exam Focus

• Typical question patterns
  • Explain why labor demand is derived and identify what shifts it.
  • Compare a firm’s behavior in product markets vs. factor markets.
  • Interpret a scenario (change in output demand or output price) and predict the effect on a factor market.
• Common mistakes
  • Treating factor demand like consumer demand (forgetting it depends on marginal productivity and product price).
  • Mixing up who supplies what (households supply factors; firms demand factors).
  • Assuming factor demand depends only on wages, ignoring output price and productivity.

The Production Link: Marginal Product and Diminishing Returns

To understand factor demand, you need a clear model of how inputs turn into output. Firms choose inputs using marginal analysis: they compare the additional benefit from one more unit of input to the additional cost.

Marginal product (MP): what it means

The marginal product of labor is the additional output produced by hiring one more unit of labor (for example, one more worker or one more hour), holding other inputs fixed.

MP_L = \frac{\Delta Q}{\Delta L}

• \Delta Q is the change in quantity of output.
• \Delta L is the change in labor used.

You can define marginal product for any input (capital, land), but labor is the main focus in AP Micro.

Diminishing marginal returns: why MP often falls

In the short run, at least one input is fixed (often capital—machines, space, equipment). As you add more labor to a fixed amount of capital, labor becomes less effective because workers have less capital to work with or get in each other’s way. This is the law of diminishing marginal returns: beyond some point, each additional unit of a variable input adds less to output than the previous unit.

This matters because it helps explain why firms’ demand curves for labor slope downward: if the extra output from each additional worker falls, the extra revenue created by each additional worker also tends to fall.

A quick “production table” way to see MP

Suppose a bakery’s oven space is fixed in the short run. Hiring the first worker may massively increase output (someone can now run the oven all day). The second worker helps, but not as much (they share the same oven). Eventually, more workers add smaller and smaller increases to output.

This pattern—rising MP at first (specialization), then diminishing MP—shows up in many real workplaces.

Exam Focus

• Typical question patterns
  • Calculate marginal product from an output table.
  • Use diminishing marginal returns to explain the downward slope of labor demand.
  • Connect a change in capital (more machines) to changes in labor productivity.
• Common mistakes
  • Confusing marginal product with average product.
  • Forgetting “holding other inputs fixed” (MP is a short-run concept).
  • Assuming diminishing returns means output falls (output can still rise; it just rises more slowly).

Marginal Revenue Product (MRP): The Rule Firms Use to Hire Inputs

A profit-maximizing firm doesn’t hire workers because it “needs” a certain number. It hires workers as long as doing so increases profit.

Marginal revenue product: definition and intuition

The marginal revenue product of labor is the additional revenue generated by hiring one more unit of labor.

MRP_L = MR \times MP_L

• MR is marginal revenue: the extra revenue from selling one more unit of output.
• MP_L is the extra output from one more unit of labor.

This links the firm’s product market (through MR) and its production technology (through MP_L).

Competitive output markets: VMP as a special case

If the firm is a price taker in the output market (perfect competition), then:

MR = P

So:

MRP_L = P \times MP_L

This is often called the value of the marginal product of labor:

VMP_L = P \times MP_L

In perfect competition, MRP_L and VMP_L are the same number.

Profit-maximizing hiring in a perfectly competitive factor market

A wage-taking firm compares marginal benefit to marginal cost.

• Marginal benefit of labor is MRP_L.
• Marginal cost of labor is the cost of hiring one more unit of labor. In a competitive labor market, that marginal cost is the market wage (often written as wage, MFC, or MRC depending on the notation used).

The hiring rule is:

MRP_L = w

You’ll also see this summarized as MRP = MRC in perfectly competitive factor markets (meaning: hire the resource up to the point where the marginal revenue product equals the marginal resource cost). If the marginal cost of the resource exceeds its marginal revenue product, the firm will not hire that unit because it would reduce profit.

Why the firm’s labor demand curve is its MRP curve

If wages fall, the equality MRP_L = w occurs at a larger quantity of labor; if wages rise, it occurs at a smaller quantity. So a firm’s **demand for labor** is its MRP_L curve (for a wage-taking firm). Because marginal product tends to diminish, MRP_L tends to slope downward.

Worked example: hiring using MRP

Suppose a competitive firm sells output at price P = 10. The firm’s marginal products for each additional worker are:

Compute MRP_L = P \times MP_L:

• Worker 1: MRP = 10 \times 8 = 80
• Worker 2: MRP = 10 \times 6 = 60
• Worker 3: MRP = 10 \times 4 = 40
• Worker 4: MRP = 10 \times 2 = 20

If the wage is w = 45, hire workers whose MRP is at least 45:

• Hire worker 1 (80) and worker 2 (60).
• Do not hire worker 3 (40) or worker 4 (20).

So the optimal labor quantity is 2 workers.

What shifts a firm’s labor demand (MRP)

Since MRP_L = MR \times MP_L, labor demand shifts when either piece changes:

1) Changes in output price or marginal revenue

• If output price rises in perfect competition, P rises, so MRP_L rises at every quantity of labor.

2) Changes in productivity

• Better training, more capital, improved technology, or better management can increase MP_L.

3) Changes in complementary inputs

• If capital and labor are complements, more capital increases labor productivity and raises MRP_L.

Exam Focus

• Typical question patterns
  • Calculate MP_L and MRP_L from a table and determine optimal hiring for a given wage.
  • Explain why the firm’s labor demand curve slopes downward.
  • Identify and graph a shift in labor demand after a change in output price or productivity.
• Common mistakes
  • Using P when the firm is not in a competitive output market (you must use MR in general).
  • Hiring where MP_L = w instead of where MRP_L = w.
  • Treating a movement along the MRP_L curve (wage change) as a shift (productivity/output price changes shift it).

When the Firm Has Market Power in the Output Market: MRP Uses MR, Not Price

Many AP questions test whether you remember that MRP_L depends on marginal revenue, not necessarily price.

Monopoly (or imperfect competition) changes MR

If the firm is a price maker in the output market, it faces a downward-sloping demand curve, so to sell more output it must lower price. As a result:

• MR < P for a monopolist (over the relevant range).

So the correct formula is still:

MRP_L = MR \times MP_L

If MR is lower than P, then MRP_L is lower than it would be under perfect competition with the same MP_L.

Consequence: less labor hired (all else equal)

If the firm is still a wage taker in the labor market, it hires where MRP_L = w. A lower MRP_L means that equality occurs at a smaller quantity of labor. So compared to a competitive firm with the same production technology, a monopolist typically hires fewer inputs and produces less output.

Example: same MP, different output market

Suppose MP_L = 5 for the next worker.

• In perfect competition with P = 10, MRP = 10 \times 5 = 50.
• In monopoly where MR = 7, MRP = 7 \times 5 = 35.

If w = 40, the competitive firm would hire (50 >= 40), but the monopolist would not (35 < 40).

Exam Focus

• Typical question patterns
  • Compare hiring decisions when the firm is a perfect competitor vs. monopolist in the output market.
  • Given P and MR (or a demand schedule), compute MRP and hiring.
  • Explain why factor demand is lower under monopoly.
• Common mistakes
  • Automatically substituting P for MR even when the firm is not perfectly competitive.
  • Thinking monopoly changes MP_L directly (it changes MR; productivity is separate).
  • Confusing the firm’s labor demand with the market labor demand (market demand is horizontal sum across firms).

Choosing the Cost-Minimizing Combination of Inputs (Least-Cost Rule)

Firms don’t only decide how much labor to hire; they also decide the best mix of inputs (especially labor and capital) to produce a given level of output at the lowest possible cost.

Least-cost rule (how firms choose between labor and capital)

The least cost rule says that a firm minimizes the cost of producing a given output when the marginal product per dollar spent is equalized across inputs:

\frac{MP_L}{P_L}=\frac{MP_K}{P_K}

• MP_L is marginal product of labor; P_L is the price of labor (the wage).
• MP_K is marginal product of capital; P_K is the price of capital (the rental rate).

Interpreting the rule (the “buy more of the higher ratio” logic)

If one side is larger, the firm is getting more additional output per dollar from that input. The cost-minimizing response is:

• Buy more of the input with the higher marginal product per dollar.
• Buy less of the input with the lower marginal product per dollar.

As the firm buys more of an input, diminishing marginal returns tends to push that input’s marginal product down, which is why the ratios can move toward equality as the firm adjusts.

Exam Focus

• Typical question patterns
  • Given MP_L, MP_K, wage, and rental rate, decide whether the firm should use more labor or more capital.
  • Explain how diminishing marginal returns helps push firms toward the least-cost combination.
• Common mistakes
  • Using total product instead of marginal product in the ratio.
  • Forgetting that the “price” in the denominator is the input’s per-unit cost (wage or rental rate).
  • Thinking least-cost input choice is the same decision as profit-maximizing hiring (least-cost is about input mix; profit-maximizing hiring is about comparing MRP to input cost).

Labor Supply: How Workers Decide Whether (and How Much) to Work

So far you’ve focused on firms’ demand for labor. But wages in a labor market depend on both demand and supply.

The meaning of labor supply

Labor supply is the relationship between the wage rate and the quantity of labor workers are willing and able to provide. At the individual level, a worker is allocating time between:

• work (earning income), and
• leisure (time not working: rest, family, hobbies, school).

Higher wages make work more attractive, but they also make workers wealthier—which can increase the desire for leisure.

Substitution effect and income effect

When the wage rises:

1) Substitution effect (toward work)

• Leisure becomes more “expensive” because each hour of leisure now costs you more foregone wages.
• This tends to increase labor supplied.

2) Income effect (toward leisure)

• With a higher wage, you can reach a desired income with fewer hours.
• This can reduce labor supplied.

At relatively low wages, the substitution effect often dominates (labor supply slopes upward). At high wages, the income effect can dominate, creating a backward-bending labor supply for an individual.

AP questions are usually careful about whether they mean:

• an individual’s labor supply (where backward-bending is possible), or
• the market labor supply (often upward sloping because it aggregates many workers with different preferences and opportunities).

Reservation wage and participation

A key idea in labor supply is a reservation wage: the lowest wage at which a person is willing to work. If the market wage is below a person’s reservation wage, they supply zero labor.

Changes in the reservation wage can shift labor supply:

• If the cost of living rises, a worker may accept work at lower wages (reservation wage falls), increasing labor supply.
• If non-labor income rises (financial support, benefits, wealth), reservation wage may rise, reducing labor supply.

Non-wage factors that shift labor supply

Market labor supply can shift due to:

• Population changes (growth, aging, migration)
• Preferences and social norms (including personal values and changing participation)
• Intervention by government (policies that affect willingness/ability to work)
• Education and training requirements (licensing and credentials can reduce supply)
• Working conditions and job attributes (risk, flexibility, location)

Many jobs must pay a compensating wage differential—extra wage—to attract workers to unpleasant or risky jobs.

Exam Focus

• Typical question patterns
  • Identify whether a scenario affects labor supply or labor demand.
  • Explain an individual’s labor supply response using substitution and income effects.
  • Predict how immigration, licensing requirements, or changes in preferences shift market labor supply.
• Common mistakes
  • Treating backward-bending supply as the standard market supply (it’s mainly an individual story).
  • Confusing a movement along supply (wage change) with a shift (non-wage changes).
  • Assuming higher wages always increase labor supplied (income effect can offset at high wages for individuals).

Competitive Labor Market Equilibrium and Wage Determination

A competitive labor market is one where many firms compete to hire workers and many workers compete for jobs, so no single employer or worker can set the wage. In that setting, wage is determined by the intersection of market supply and market demand for labor—the standard supply and demand model.

Where market labor demand comes from

Market labor demand is the horizontal sum of all firms’ labor demand curves. Since each firm’s labor demand curve is its MRP_L curve, market demand reflects productivity of workers across firms, output prices (or marginal revenues), and the number of firms and their technologies.

Equilibrium wage and employment

In equilibrium, the wage adjusts until quantity of labor supplied equals quantity of labor demanded. The equilibrium wage in the market establishes the wage that firms will pay workers.

A crucial implication: in a competitive labor market, the wage tends to equal the marginal revenue product for the last unit of labor hired. For an individual firm that is a wage taker, the wage is “given,” and the firm hires where:

MRP_L = w

5.2-style checklist: determinants of labor demand and labor supply

A fast way to organize shifts (these factors determine the supply and demand of labor quantities):

Shifts in competitive labor demand (real-world intuition)

Because labor demand is derived, it shifts when product markets or productivity change:

• Output price increases: raises MRP_L in competitive output markets, shifting labor demand right.
• Product demand increases: typically raises output price and/or quantity sold, increasing labor demand.
• Productivity increases (technology, training, more capital): shifts demand right.
• Change in prices of related inputs:
  • If capital and labor are complements: cheaper capital increases capital use, raises MP_L, shifting labor demand right.
  • If capital and labor are substitutes: cheaper capital may replace labor, shifting labor demand left.

Example: shift analysis in a competitive labor market

Suppose there’s a boom in demand for home renovations.

• Construction firms can sell more output (and often at better prices).
• That increases the marginal revenue product of carpenters.
• Market demand for carpenters shifts right.

Prediction: equilibrium wage and employment for carpenters rise.

Wage differences across jobs: not always “unfair,” often economic

In competitive models, different wages can arise because:

• different jobs require different skills and education (human capital)
• different jobs have different non-wage attributes (risk, location)
• supply differs (few qualified workers means higher wages)
• demand differs (high marginal revenue product occupations)

AP questions may describe two occupations and ask why wages differ. A strong answer ties the difference to either differences in labor demand (higher MRP) or differences in labor supply (training barriers, unpleasant conditions).

Exam Focus

• Typical question patterns
  • Given a change in product demand or technology, identify how labor demand shifts and how equilibrium wage/employment change.
  • Explain wage differentials using supply/demand, human capital, and compensating differentials.
  • Connect the market wage to the firm’s hiring rule MRP_L = w.
• Common mistakes
  • Saying “demand for labor increases because wages increased” (wage changes cause movements along demand).
  • Forgetting that higher productivity shifts labor demand right even if wages are unchanged.
  • Explaining wage differences using only “fairness” language without supply/demand mechanisms.

Monopsony in the Labor Market: When a Single Buyer Has Wage-Setting Power

A monopsony is a market with a single buyer. In labor markets, that means many sellers (workers), one buyer (employer). This is a form of imperfect competition in the factor market. A monopsonist employer might be the dominant (or only) hirer of a type of labor in an area—like a large hospital system in a small town hiring most nurses.

The key difference from competition: in monopsony, the firm faces the upward-sloping market labor supply curve.

Why marginal factor cost exceeds the wage in monopsony

In a competitive labor market, a firm can hire more workers without raising the wage (it is a wage taker). In monopsony, to attract additional workers the firm must offer a higher wage.

But if hiring more workers requires raising the wage, the firm often ends up paying a higher wage to all (or many) of its workers. That means the marginal factor cost (the additional cost of an additional resource/worker) is greater than the wage.

• In monopsony, MFC > w for additional workers.
• Graphically, the MFC curve lies above the labor supply curve.

The monopsonist hiring rule

The firm still compares marginal benefit to marginal cost, but marginal cost is MFC, not w:

MRP_L = MFC

After choosing the profit-maximizing quantity of labor from that rule, the monopsonist then pays the wage determined by the labor supply curve at that quantity.

Outcome compared to competition

Relative to a competitive labor market, monopsony typically results in:

• lower employment
• lower wages

Worked example: monopsony with a labor supply schedule

Suppose a firm faces this labor supply (wage needed to hire each quantity):

Total labor cost at each employment level is wage times workers:

• 1 worker: total cost = 10
• 2 workers: total cost = 24
• 3 workers: total cost = 42
• 4 workers: total cost = 64

Now compute MFC as the change in total cost:

• Hiring 2nd worker: MFC = 24 - 10 = 14
• Hiring 3rd worker: MFC = 42 - 24 = 18
• Hiring 4th worker: MFC = 64 - 42 = 22

Suppose MRP_L for each worker is:

Choose labor where MRP_L is at least MFC:

• 2nd worker: MRP = 18 vs MFC = 14 → hire
• 3rd worker: MRP = 16 vs MFC = 18 → do not hire

So the monopsonist hires 2 workers and pays the wage needed for 2 workers, which is 12.

Notice what happened: the marginal cost of the 2nd worker was 14 (because wage increases for both workers), but each worker is only paid 12.

Minimum wage in a monopsony (a subtle but common test)

In a competitive market, a binding minimum wage creates unemployment. In a monopsony, a properly set minimum wage can sometimes increase both wages and employment.

Why? If the government sets a minimum wage slightly above the monopsonist’s wage, the firm may be able to hire more workers at that wage without having to raise wages further for each additional worker (up to some point). Over that range, MFC can fall compared to the original monopsony MFC.

You must always analyze the specific graph: if the minimum wage is set too high, it can still reduce employment even in monopsony.

Exam Focus

• Typical question patterns
  • Identify monopsony and explain why MFC lies above labor supply.
  • Determine the monopsony employment level using MRP_L = MFC and then find the wage from supply.
  • Analyze the effect of a minimum wage in monopsony vs. competition.
• Common mistakes
  • Setting MRP_L = w in monopsony (you must use MRP_L = MFC).
  • Thinking monopsony means “one seller” (that’s monopoly; monopsony is one buyer).
  • Assuming any minimum wage raises employment in monopsony (only within a certain range).

Labor Market Interventions: Minimum Wage, Unions, and Payroll Taxes

Real labor markets often include institutions and policies that affect wages and employment.

Minimum wage (competitive labor market)

A minimum wage is a price floor in the labor market. In a competitive labor market, if the minimum wage is set above equilibrium, it becomes binding.

Mechanism:

• At a higher wage, more workers want to work (quantity supplied rises).
• Firms want to hire fewer workers (quantity demanded falls).
• The gap is unemployment (a surplus of labor).

A strong AP explanation uses the words “surplus of labor” and connects it to movements along supply and demand.

Unions (collective bargaining)

A labor union is an organization of workers that negotiates with employers over wages and working conditions. In basic models, a union can increase wages above competitive equilibrium.

How unions can raise wages:

• If the union has bargaining power, it can act like a “seller with market power” over labor.
• A higher negotiated wage can reduce quantity of labor demanded by firms, potentially creating unemployment (fewer jobs available at that wage).

But unions may also increase productivity (better training, reduced turnover) in ways that can increase MP_L and therefore increase MRP_L. Some scenarios include both a wage increase and a productivity increase, so you have to track both.

Payroll taxes and tax incidence in the labor market

A payroll tax is a tax on labor. It can be levied on employers, employees, or both. The key economic idea is that the side of the market that is more inelastic bears more of the tax burden, regardless of who formally pays.

In a labor market graph, a tax creates a wedge between:

• the wage firms pay (including the tax), and
• the wage workers receive (after the tax).

Employment typically falls because the tax raises the cost of labor to firms or lowers the effective wage to workers.

Exam Focus

• Typical question patterns
  • Graph a binding minimum wage and identify unemployment.
  • Explain union wage effects using labor supply/demand (and possibly shifts in demand if productivity changes).
  • Analyze a payroll tax and determine who bears more burden using relative elasticities.
• Common mistakes
  • Calling unemployment from minimum wage a shortage (it’s a surplus of labor).
  • Forgetting that union wage increases can reduce employment unless labor demand shifts.
  • Treating statutory incidence (who sends the tax) as economic incidence (who bears the burden).

Factor Markets Beyond Labor: Land (Rent) and Capital (Rental Rate)

While labor is the main focus, the same logic applies to any input: firms hire an input up to the point where marginal benefit equals marginal cost.

The general rule for any factor

For any resource input, marginal benefit from one more unit is its marginal revenue product:

MRP = MR \times MP

In competitive output markets:

MRP = P \times MP

If the input market is competitive (the firm is a price taker for the input), the marginal cost of the input is simply its market price (wage for labor, rent for land, rental rate for capital). So the general hiring rule is:

MRP = \text{input price}

Land and rent

Land includes natural resources and location. The payment to landowners is rent.

Rent exists largely because land is often fixed in supply (or highly inelastic), especially in a specific location. When supply is inelastic, changes in demand can have large effects on rent.

Demand for land is derived from what the land can produce or enable:

• farmland demand depends on crop prices and productivity
• downtown retail space demand depends on consumer traffic and retail revenue

If demand for output rises, the derived demand for land can rise, increasing rent.

Capital and the rental rate

In AP Micro, capital typically means physical capital (machines, tools, buildings). Firms often face a rental rate of capital—the cost per period of using capital.

A firm demands capital up to the point where the extra revenue created by one more unit of capital equals the rental rate. This mirrors labor:

• replace MP_L with MP_K
• replace wage with rental rate

Substitutes and complements among inputs

A big part of factor markets is understanding how one input’s market affects another:

• Complementary inputs: used together. If the price of one falls, firms use more of it, which can increase demand for the other.

  • Example: better (cheaper) computer equipment can raise the productivity of software engineers, increasing demand for engineers.

• Substitute inputs: can replace each other. If the price of one falls, firms use more of it and less of the other.

  • Example: cheaper automation equipment can reduce demand for certain routine labor tasks.

These relationships show up as shifts in factor demand curves.

Exam Focus

• Typical question patterns
  • Apply the MRP = \text{input price} rule to land or capital (not just labor).
  • Predict how a change in output price affects rent or the rental rate.
  • Determine whether two inputs are substitutes or complements and explain how a price change shifts factor demand.
• Common mistakes
  • Treating rent as purely “greed” rather than derived demand plus (often) inelastic supply.
  • Assuming capital demand always rises with wages (it depends on whether capital substitutes for or complements labor).
  • Mixing up “capital” (machines) with “money” (financial capital); in AP Micro factor markets, the focus is usually physical capital services.

Elasticity and Factor Demand: When Wages Change, How Much Does Hiring Respond?

Some labor markets respond strongly to wage changes, while others barely respond. That difference is captured by the elasticity of demand for labor.

Why elasticity matters

Elasticity helps you predict:

• how much employment changes when wages rise (due to minimum wage, unions, taxes)
• who bears the burden of payroll taxes
• how quickly firms substitute capital for labor

Even if you don’t compute numeric elasticities, you’re often expected to reason about “more elastic” vs. “more inelastic.”

Key determinants of elasticity of demand for labor

1) Elasticity of demand for the final product

• If consumer demand for the product is elastic, a wage increase that raises costs and price can cause a large drop in quantity sold, reducing labor demand more.

2) Ease of substituting other inputs for labor

• If capital can easily replace labor (high substitutability), labor demand is more elastic.

3) Labor’s share of total costs

• If labor is a large fraction of total costs, a wage increase significantly raises marginal cost, so firms cut labor more.

4) Time horizon

• In the long run, firms can adjust production methods and substitute inputs more easily, making labor demand more elastic.

Example reasoning (no heavy math required)

Compare two jobs:

• Cashiers in a fast-food restaurant: tasks may be automatable, so labor demand can be relatively elastic over time.
• Specialized nurses in an ICU: fewer close substitutes and high skill requirements, so demand can be more inelastic.

If wages rise, the fast-food firm may reduce cashier hours or adopt kiosks; the ICU still needs nurses.

Exam Focus

• Typical question patterns
  • Given a policy (minimum wage or tax), predict whether employment falls a lot or a little using elasticity reasoning.
  • Compare two labor markets and explain which has more elastic labor demand.
  • Connect substitutability/time horizon to elasticity.
• Common mistakes
  • Confusing elasticity of labor demand with elasticity of labor supply.
  • Saying “if wages rise, demand becomes elastic” (elasticity is about responsiveness, not the direction of change).
  • Ignoring the role of substitution possibilities and time.

Putting It All Together: Multi-Step AP-Style Scenarios

Many Unit 5 questions are multi-step: a change starts in one market (product market, technology, policy) and you trace effects into the factor market.

Scenario 1: output price increase in a competitive product market

Suppose the market price of widgets rises.

Step 1: For a competitive firm, MR = P, so higher P increases MR.

Step 2: Since MRP_L = P \times MP_L, higher P raises MRP_L at every labor quantity.

Step 3: The firm’s labor demand (its MRP_L curve) shifts right.

Step 4: In the market labor graph, labor demand shifts right, raising equilibrium wage and employment.

Common pitfall: saying “labor demand increases because wage increased.” The wage increases as an outcome of demand shifting; it is not the cause of the shift.

Scenario 2: a productivity improvement from new capital equipment

Suppose firms adopt a new machine that makes each worker more productive.

Step 1: MP_L increases.

Step 2: MRP_L = MR \times MP_L increases.

Step 3: Labor demand shifts right.

This is a good reminder that capital can increase labor demand when labor and capital are complements.

Scenario 3: minimum wage in monopsony vs. competition

If you’re told “the labor market is monopsonistic,” your default model must change:

• The firm hires where MRP_L = MFC, not where MRP_L = w.

Then a minimum wage can flatten the marginal cost of labor over some range, potentially increasing employment.

Worked problem: tracing a chain with numbers

A competitive firm sells output at P = 20. Initially, a worker’s marginal product is MP_L = 3, so:

MRP_L = 20 \times 3 = 60

If the wage is w = 50, the firm hires that worker because MRP_L > w.

Now suppose output price falls to P = 15, with productivity unchanged:

MRP_L = 15 \times 3 = 45

Now MRP_L < w, so the firm will reduce labor hired (or not hire that marginal worker). In market terms, labor demand decreases because the derived demand fell when output price fell.

Exam Focus

• Typical question patterns
  • “Shock in product market” → determine shift in MRP → shift in factor demand → new wage/employment.
  • Compare outcomes under competitive labor market vs. monopsony.
  • Use a table to compute MP and MRP before and after a change.
• Common mistakes
  • Skipping the MRP step and jumping straight to wage conclusions without mechanism.
  • Using the wrong market structure assumption (treating monopoly like perfect competition in MR).
  • Confusing shifts in labor demand with movements along labor demand when wage changes.