MSE 263: Managerial Economics

Sources and References

Primary textbook — Jeffrey M. Perloff & James A. Brander, Managerial Economics and Strategy, 3rd ed. (Pearson Canada, 2020). Supplementary texts — Robert S. Pindyck & Daniel L. Rubinfeld Microeconomics; Hal R. Varian Intermediate Microeconomics: A Modern Approach; Jean Tirole The Theory of Industrial Organization. Online resources — MIT OpenCourseWare 14.01 “Principles of Microeconomics”; Khan Academy Microeconomics.

Chapter 1 — Economics and Managerial Decision-Making

Managerial economics applies microeconomic reasoning to the decisions a firm’s manager must make: what to produce, how much to produce, what to charge, whether to enter a market, and how to respond to rivals. Perloff and Brander frame the discipline as the study of constrained optimization under scarcity, where the constraint may be a budget, a production technology, a contract, or the strategic behaviour of competitors. The manager’s objective is typically to maximize profit, though agency and behavioural considerations mean real decision-makers also pursue reputation, market share, or growth.

A central organizing idea is opportunity cost: the value of the next-best alternative foregone. Economic profit subtracts all opportunity costs, including the return the owner could have earned by deploying capital and labour elsewhere, whereas accounting profit counts only explicit cash expenses. A firm with positive accounting profit but negative economic profit is destroying value relative to its alternatives. Sunk costs, by contrast, are irrelevant to forward-looking decisions; once incurred, they cannot be recovered and should not influence marginal choices.

Rational decision-making relies on marginal analysis: push any activity to the point where marginal benefit equals marginal cost. Hire another worker if the extra revenue from their output exceeds the extra wage bill. Produce another unit if marginal revenue meets marginal cost. The rule is simple, but its application requires careful identification of which costs and benefits truly change at the margin.

Gains from trade, introduced by Perloff and Brander alongside the preliminaries, formalize why voluntary exchange creates value. If two parties value a good differently — because of differing endowments, preferences, or productivities — a trade at any price between their valuations makes both better off. Ricardo’s principle of comparative advantage extends the idea: even a party absolutely less productive at everything gains by specializing in what it does relatively best. For a manager, comparative advantage explains outsourcing, vertical specialization, and the make-or-buy decision.

Managerial economics thus combines a toolbox — demand, cost, market-structure, and game-theoretic models — with a disciplined way of asking, at every decision point, what the relevant marginal trade-off is.

Chapter 2 — Supply, Demand, and Market Equilibrium

A demand curve describes how much of a good consumers wish to buy at each price, holding income, tastes, and other prices fixed. Its typical downward slope follows from the law of demand: as price falls, quantity demanded rises through substitution (the good becomes cheaper relative to alternatives) and income effects (real purchasing power expands). A supply curve shows how much producers wish to sell at each price; it usually slopes up because higher prices cover the marginal cost of bringing additional, less-efficient units to market.

Market equilibrium is the price \( P^* \) and quantity \( Q^* \) at which quantity supplied equals quantity demanded. Writing linear schedules \( Q_d = a - bP \) and \( Q_s = c + dP \), equilibrium satisfies

\[ P^* = \frac{a - c}{b + d}, \qquad Q^* = \frac{ad + bc}{b + d}. \]

Above \( P^* \), surplus inventory pressures sellers to cut prices; below \( P^* \), shortages let sellers raise them.

Comparative statics ask how equilibrium moves when an exogenous variable changes. An increase in consumer income shifts demand right for a normal good, raising both price and quantity. A new production technology shifts supply right, lowering price and raising quantity. A per-unit tax \( t \) on sellers acts like an upward shift in supply by \( t \); the resulting tax incidence falls more heavily on whichever side of the market is less price-sensitive.

Consumer surplus is the area between the demand curve and the price line — the cumulative difference between willingness to pay and actual payment. Producer surplus is the area between the price line and the supply curve. In a competitive equilibrium, the sum is maximized, which is the welfare-theoretic reason economists treat competitive markets as a benchmark.

Price controls illustrate what happens when equilibrium is overridden. A binding price ceiling below \( P^* \) causes shortages, queuing, and a deadweight loss; a binding price floor above \( P^* \) causes surpluses. For managers, the supply-and-demand framework is the first filter for any question about how a market will respond to cost shocks, entry, regulation, or macro conditions.

Chapter 3 — Elasticity of Demand and Supply

Elasticity measures the responsiveness of one variable to another, normalized to percentages so the measure is unit-free. The own-price elasticity of demand is

\[ \varepsilon = \frac{\partial Q}{\partial P} \cdot \frac{P}{Q}. \]

Demand is elastic when \( |\varepsilon| > 1 \), inelastic when \( |\varepsilon| < 1 \), and unit-elastic when \( |\varepsilon| = 1 \). Along a linear demand curve, elasticity varies from infinity at the price intercept to zero at the quantity intercept, so “the” elasticity must be quoted at a specific point or averaged over a range.

Elasticity governs how revenue responds to a price change. Because total revenue \( R = PQ \), a small price increase raises revenue when demand is inelastic and lowers it when demand is elastic. At the revenue-maximizing price, demand is unit-elastic. This gives managers a quick diagnostic: if a price cut increases revenue, demand at the current price is elastic.

The cross-price elasticity \( \varepsilon_{xy} = (\partial Q_x / \partial P_y)(P_y / Q_x) \) is positive for substitutes and negative for complements. The income elasticity \( \eta = (\partial Q / \partial I)(I / Q) \) is positive for normal goods, negative for inferior goods, and above one for luxuries. Advertising elasticity captures demand’s response to marketing spend.

Determinants of elasticity include the availability of close substitutes, the share of income the good absorbs, whether the good is a necessity or a luxury, and the time horizon. Gasoline demand is nearly inelastic in the short run because vehicles are fixed, but much more elastic over years as consumers switch to efficient cars or transit. Managers therefore distinguish short-run pricing elasticity from long-run elasticity when forecasting volume responses.

The price elasticity of supply measures producers’ responsiveness. It depends on the flexibility of inputs, capacity utilization, and the planning horizon. Together, demand and supply elasticities determine tax incidence, the size of deadweight losses, and the volume impact of any price move a firm contemplates.

Chapter 4 — Consumer Choice: Utility, Budgets, and Preferences

Consumer theory models a buyer who ranks consumption bundles and chooses the best one affordable. Preferences are assumed complete, transitive, and monotonic (more is better for goods). A utility function \( U(x_1, x_2) \) is a convenient numerical representation, though only the ordering matters. Indifference curves trace bundles that give equal utility; their slope, the marginal rate of substitution (MRS), equals the ratio of marginal utilities:

\[ \mathrm{MRS} = \frac{MU_1}{MU_2}. \]

Convex indifference curves reflect diminishing MRS: the more of a good one has, the less of the other one is willing to give up for an extra unit.

The budget constraint \( p_1 x_1 + p_2 x_2 = I \) pins down affordable bundles. Its slope \( -p_1/p_2 \) is the market rate of exchange. Optimal choice requires the MRS equal the price ratio:

\[ \frac{MU_1}{MU_2} = \frac{p_1}{p_2}, \]

equivalently, the marginal utility per dollar is equalized across goods. Geometrically, the highest reachable indifference curve is tangent to the budget line.

A price change decomposes into a substitution effect — along the original indifference curve, always toward the cheaper good — and an income effect — from the change in real purchasing power. For normal goods both effects push the same way; for inferior goods they oppose, and for rare Giffen goods the income effect dominates.

Aggregating individual demands by horizontal summation yields the market demand curve that anchors Chapter 2. Willingness to pay equals the height of the demand curve, which is why consumer surplus measures welfare. Managers use consumer theory both as a foundation (why demand slopes down, how cross-effects arise) and as a practical tool for segmentation: different groups have different MRS, so targeted offers can extract surplus that uniform prices cannot. Concepts from this chapter reappear in price discrimination, bundling, and the design of loyalty programs.

Chapter 5 — Production and the Production Function

A production function \( Q = f(L, K) \) links output to inputs such as labour \( L \) and capital \( K \). In the short run at least one input — typically capital — is fixed; in the long run all inputs vary. The short-run decision is how much variable input to use given the fixed plant; the long-run decision is how to build the plant itself.

The marginal product of labour is \( MP_L = \partial Q / \partial L \). The law of diminishing marginal returns states that, holding other inputs fixed, \( MP_L \) eventually falls as more \( L \) is added: each additional worker has less capital to work with. Total product rises, then flattens. Average product \( AP_L = Q / L \) is cut by marginal product: when \( MP_L > AP_L \), average is rising; when \( MP_L < AP_L \), average is falling.

In the long run, isoquants show input combinations yielding equal output, analogous to indifference curves. Their slope, the marginal rate of technical substitution (MRTS), equals \( MP_L / MP_K \). Cost-minimizing input choice equates MRTS to the input price ratio:

\[ \frac{MP_L}{MP_K} = \frac{w}{r}, \]

so the marginal product per dollar is equalized across inputs. This is the producer’s analogue of equalizing marginal utility per dollar.

Returns to scale describe what happens when all inputs scale proportionally. Increasing returns \( (f(\lambda L, \lambda K) > \lambda f(L,K)) \) arise from specialization, indivisibilities, and network effects; constant returns are the benchmark; decreasing returns arise from coordination limits. Returns to scale are distinct from diminishing marginal returns, which hold some inputs fixed.

Technical progress shifts the production function outward: the same inputs produce more output, or the same output requires fewer inputs. For managers, production theory disciplines thinking about capacity planning, input mix, automation versus labour, and where returns to scale support consolidation.

Chapter 6 — Short-Run and Long-Run Costs

Cost curves translate the production function into dollar terms given input prices. In the short run, total cost \( TC = FC + VC(Q) \) splits into fixed and variable parts. Dividing by quantity gives average fixed cost \( AFC = FC/Q \), average variable cost \( AVC = VC/Q \), and average total cost \( ATC = TC/Q \). Marginal cost \( MC = dTC/dQ \) is the extra cost of one more unit.

Two geometric facts drive the rest of the theory. First, because only variable cost changes at the margin, \( MC = dVC/dQ \). Second, the MC curve cuts both AVC and ATC at their minima: when marginal is below average, the average is falling; when marginal is above average, the average is rising. These relationships mirror the product-curve geometry of Chapter 5; they are dual.

Short-run ATC curves are typically U-shaped: AFC falls steadily as fixed costs are spread, while AVC eventually rises as diminishing marginal returns push MC up. The minimum of ATC defines the plant’s efficient scale. In the long run, the firm chooses the plant itself; the long-run average cost (LRAC) curve is the lower envelope of all short-run ATCs. LRAC may exhibit:

• Economies of scale — LRAC falling as output expands, from specialization, bulk discounts, spreading of R&D, and learning.
• Constant returns — a flat region at minimum efficient scale (MES).
• Diseconomies of scale — LRAC rising, from coordination, bureaucracy, and communication costs.

MES, compared with market size, determines how many firms can coexist. When MES is a large share of demand, the market supports few firms (tending toward oligopoly or monopoly). When MES is tiny relative to demand, many firms fit.

Economies of scope arise when joint production of multiple goods is cheaper than separate production, often because of shared inputs. Learning curves cause average cost to fall with cumulative output, which is distinct from economies of scale and motivates aggressive early pricing in markets where experience matters. Managers use these concepts to decide plant size, product breadth, and pricing over a product’s life cycle.

Chapter 7 — Perfect Competition: Firm and Industry

Perfect competition is the benchmark market structure. Its assumptions — many small buyers and sellers, homogeneous product, free entry and exit, full information, and no transaction costs — imply that each firm is a price taker: it faces a horizontal demand curve at the market price because any attempt to charge more loses all customers, and charging less is pointless. Marginal revenue equals price: \( MR = P \).

The profit-maximizing rule \( MR = MC \) becomes \( P = MC \) for the competitive firm. If at that quantity \( P > ATC \), the firm earns positive economic profit; if \( P < ATC \) but \( P > AVC \), it produces at a loss but covers variable costs and part of fixed cost, so it is better to operate than shut down. If \( P < AVC \), the firm should shut down in the short run. The short-run supply curve of the firm is thus the portion of \( MC \) above minimum AVC.

In the long run, entry and exit drive economic profit to zero. When profits are positive, new firms enter, industry supply shifts right, and price falls; when profits are negative, firms exit, supply shifts left, and price rises. Equilibrium requires \( P = ATC_{\min} \), so each surviving firm produces at minimum average cost. The long-run industry supply curve may be flat (constant-cost industry), upward-sloping (increasing-cost), or downward-sloping (decreasing-cost), depending on how input prices respond to industry expansion.

Welfare in competitive equilibrium is maximized in the sense that consumer plus producer surplus is as large as possible: the marginal value to consumers equals the marginal cost to producers for the last unit. Any deviation — taxes, price controls, market power — creates deadweight loss.

Perfect competition is a model, not a literal description of real markets; few industries meet all its assumptions. But it clarifies the forces at work. When managers face commodity-like products, near-zero switching costs, low entry barriers, or transparent pricing, the competitive model predicts outcomes well: margins compressed toward cost, no pricing discretion, and survival dependent on operating at MES.

Chapter 8 — Monopoly and Monopoly Power

A monopolist is the sole seller of a product with no close substitutes, protected by some barrier to entry — a patent, a unique resource, a network effect, a regulatory franchise, or natural economies of scale large enough to make one firm cheapest. Unlike the competitive firm, the monopolist faces the entire downward-sloping market demand. To sell one more unit it must lower price on all units (absent discrimination), so marginal revenue lies below price:

\[ MR = P\left(1 + \frac{1}{\varepsilon}\right), \]

where \( \varepsilon < 0 \) is the price elasticity of demand.

Profit maximization still requires \( MR = MC \). Solving gives the inverse-elasticity pricing rule or Lerner index:

\[ \frac{P - MC}{P} = -\frac{1}{\varepsilon}. \]

The markup over marginal cost is larger the less elastic demand is. A monopolist will never operate on the inelastic portion of demand (where \( |\varepsilon| < 1 \)), because cutting output and raising price would both raise revenue and cut cost. Equivalently, optimal monopoly price is a fixed markup above marginal cost, given elasticity.

Monopoly creates deadweight loss: the monopolist produces less than the competitive quantity, and units worth more to consumers than their marginal cost go unproduced. Consumer surplus shrinks; part is transferred to the monopolist as profit, and part is lost entirely. Beyond static losses, monopoly can entail rent-seeking costs (resources spent acquiring or protecting the monopoly) and X-inefficiency (slack management where competitive pressure is absent). Offsetting benefits may include funding for R&D that a fragmented industry could not sustain, which is one rationale for patents.

Sources of market power include legal barriers, cost advantages, essential input control, product differentiation creating brand-level monopoly, and switching costs. Most real firms with pricing power are not pure monopolists but hold some degree of power; the Lerner index, estimated from the firm’s perceived elasticity, measures that power in a way the manager can act on. The ability to set \( P > MC \) is the economic definition of market power, and it appears wherever customers are locked in, misinformed, or lacking substitutes.

Chapter 9 — Price Discrimination and Bundling

A single posted price leaves money on the table: some buyers would have paid more, others would buy at a lower price but not the single one. Price discrimination captures some of this foregone surplus by charging different customers different prices for essentially the same good. Three conditions are required: market power, the ability to segment consumers by willingness to pay, and the ability to prevent resale between segments.

First-degree (perfect) price discrimination charges each buyer their exact willingness to pay. The outcome produces the efficient quantity — every unit whose value exceeds marginal cost is sold — but all surplus accrues to the seller. It is an idealization, approached by one-off negotiated deals.

Second-degree discrimination uses nonlinear pricing to let customers sort themselves. Quantity discounts, two-part tariffs (a fixed access fee plus a per-unit price), block pricing, and versioning (basic versus premium features) all exploit differences in demand intensity. A two-part tariff \( T(q) = A + pq \) can approach perfect discrimination as \( A \) approaches a single consumer’s surplus at \( p = MC \).

Third-degree discrimination charges different posted prices to different identifiable groups — student discounts, senior fares, geographic pricing, airline advance purchase. The manager equalizes marginal revenue across segments, so each segment’s markup follows its own elasticity:

\[ \frac{P_i - MC}{P_i} = -\frac{1}{\varepsilon_i}. \]

Less elastic segments pay higher prices. Resale must be blocked, typically by non-transferability (ID-based discounts), service ties, or geographic isolation.

Bundling packages two or more goods at a single price. Pure bundling offers only the package; mixed bundling offers the package and the components separately. Bundling is profitable when consumer valuations across goods are negatively correlated, because the bundle price can extract surplus from buyers with diverse preference patterns that any single price on individual items cannot reach. Microsoft Office and cable-channel packages illustrate the idea. Tying — requiring purchase of product B with product A — can serve as a price-discrimination device (metering heavy users through consumption of a complement) or as an entry deterrent, which is why it draws antitrust scrutiny.

Real-world applications include couponing, loyalty programs, peak-load pricing, and dynamic pricing in airlines and hotels, all of which are variations on discrimination by observable signals of willingness to pay.

Chapter 10 — Monopolistic Competition

Monopolistic competition describes industries with many firms selling differentiated products with free entry and exit — restaurants, clothing brands, toothpaste, software apps. Each firm has some local market power because its product is not a perfect substitute for any rival’s, so it faces a downward-sloping demand curve. But because entry is easy, economic profit is competed away in the long run.

In the short run, a monopolistically competitive firm looks like a mini-monopolist: it sets \( MR = MC \), charges \( P > MC \), and may earn positive profit. Positive profits attract entry; entrants offer substitutes that steal customers, shifting each incumbent’s demand curve left and making it flatter (more elastic) because alternatives proliferate. Entry continues until demand becomes tangent to ATC at the profit-maximizing quantity: \( P = ATC \), zero economic profit, but still \( P > MC \).

Two welfare features follow. First, the long-run equilibrium occurs at a quantity below the minimum of ATC; firms operate with excess capacity. Second, because \( P > MC \), there remains a deadweight loss. Against these costs, monopolistic competition offers product variety: consumers value having many flavours, styles, and locations, and that variety has social value not captured by a simple efficiency count. Whether real markets overprovide or underprovide variety is an empirical question; the model highlights the trade-off.

Strategically, monopolistically competitive firms compete on differentiation as much as on price. Advertising, branding, design, location, and service quality all soften the elasticity of demand and prop up margins. But differentiation investments are themselves costs, and if they fail to generate durable loyalty, the firm reverts to the zero-profit condition. Long-run profits in a monopolistically competitive industry usually require either genuine barriers (a patent, a distinctive capability, a protected brand) or superior costs; without them, imitation erodes any temporary advantage.

For managers, monopolistic competition is the most common real-world structure. It explains why most firms face price-sensitive but not perfectly elastic demand, why advertising and branding matter, and why, despite pricing power, most firms earn only a normal return in the long run.

Chapter 11 — Oligopoly: Cournot, Bertrand, Stackelberg

Oligopoly is competition among a few firms, each large enough that its decisions affect rivals and vice versa. There is no single model because the outcome depends on what firms choose — quantities or prices — and on whether they move simultaneously or sequentially.

Cournot competition: firms simultaneously choose quantities, taking rivals’ quantities as given. With two symmetric firms, linear inverse demand \( P = a - b(q_1 + q_2) \), and constant marginal cost \( c \), firm 1’s profit is \( (a - b(q_1 + q_2) - c)q_1 \). The first-order condition gives the reaction function \( q_1 = (a - c - bq_2)/(2b) \). Solving symmetrically,

\[ q_1^* = q_2^* = \frac{a - c}{3b}, \qquad P^* = \frac{a + 2c}{3}. \]

Industry output is \( 2(a - c)/(3b) \), larger than monopoly \( (a - c)/(2b) \) but smaller than perfect competition \( (a - c)/b \). Cournot prices lie between monopoly and competitive levels and fall toward marginal cost as the number of firms grows.

Bertrand competition: firms simultaneously choose prices for a homogeneous good. Any firm pricing above the lowest rival sells nothing, so undercutting drives price down to \( MC \) even with just two firms — the Bertrand paradox. Differentiation, capacity constraints, or repeated interaction restore positive margins and bring the model closer to observed outcomes.

Stackelberg competition: firms choose quantities sequentially. The leader moves first, anticipating the follower’s reaction; the follower optimizes against the leader’s chosen quantity. Solving by backward induction, the leader produces more and the follower less than in Cournot, and the leader earns higher profit — the first-mover advantage. With the same linear demand,

\[ q_L = \frac{a - c}{2b}, \qquad q_F = \frac{a - c}{4b}. \]

Industry output is greater than Cournot but still below the competitive level, and price is correspondingly lower.

Collusion and cartels: oligopolists would jointly prefer the monopoly outcome but face a prisoner’s dilemma — each has incentive to cheat by expanding output. Repeated interaction and credible punishments (trigger strategies) can sustain tacit collusion, though antitrust enforcement makes explicit agreements illegal. The empirical picture is that oligopoly outcomes sit along a spectrum from near-competitive to near-monopoly depending on barriers, capacity, information, and strategic context.

Chapter 12 — Game Theory Basics for Managerial Strategy

Game theory provides the language for strategic situations where each player’s best action depends on the others’ choices. A game specifies players, their actions, the timing of moves, the information each has, and the payoffs from every outcome. Managers face games constantly: pricing against rivals, entry decisions, capacity expansion, technology adoption, and bargaining with suppliers or unions.

The central solution concept is the Nash equilibrium: a profile of strategies such that no player can raise their payoff by unilaterally deviating, given what others do. Both firms in a Cournot equilibrium play best responses to each other; neither can do better alone. Nash equilibrium does not require players to cooperate or to trust one another, only to reason through their best replies.

Strategies can be dominant (best regardless of opponents’ choices) or dominated (always worse than some alternative). Iterated elimination of dominated strategies often simplifies a game. The classic prisoner’s dilemma shows that individually rational choices can lead to collectively bad outcomes — the two-player version explains why cartels are fragile and price wars break out.

Sequential games are analyzed by backward induction: start at the last decision node and work forward, eliminating implausible threats. The Stackelberg leader’s advantage comes from commitment: its quantity, once chosen, cannot be undone, so the follower optimizes against it. Credible commitment turns sequential moves into strategic weapons — capacity expansion that would be wasteful if matched, exclusive contracts, and irreversible advertising campaigns all work by locking the player into an aggressive posture.

Repeated games create room for cooperation. In an infinitely repeated prisoner’s dilemma with sufficiently patient players, strategies like tit-for-tat or grim-trigger can sustain cooperation as an equilibrium — cheating wins a one-time gain but triggers punishment forever. The folk theorem says that for high enough discount factors, essentially any individually rational outcome can be supported. This logic underlies tacit collusion in oligopoly.

Entry and deterrence games apply these tools. An incumbent may overinvest in capacity to convince a potential entrant that accommodation would lead to ruinous post-entry competition. Whether the threat is credible — subgame perfect — depends on whether it would be the incumbent’s best response after entry actually occurs. Non-credible threats do not deter rational entrants.

Game theory does not give managers a formula; it gives a discipline. Ask who the players are, what they know, when they move, and what they can credibly commit to. Work out best responses. Look for Nash equilibria. Then ask whether commitment, reputation, repetition, or information changes the game in ways that serve the firm’s objectives. Combined with the demand, cost, and market-structure tools from the preceding chapters, this strategic lens is the core of managerial economics as Perloff and Brander present it.