Economics Essentials — CFA Level I

The classic item gives a scenario and asks whether quantity demanded or demand changed — the tell is the wording. Own-price moves you along the curve; any non-price determinant (income, tastes, expectations, prices of substitutes/complements, number of buyers) shifts the whole curve, so map each driver before answering. Vignettes that bury a substitute’s price change or an income shift are testing exactly this trap. Watch the algebra too: in the demand function Qd = a − b·P the own-price coefficient is negative; the curve you graph (price on the vertical axis) is the inverse demand function, with price written as a function of quantity. A genuinely positive own-price coefficient is the anomaly — a Giffen/Veblen good — not just inverse notation.

Don’t conflate the demand curve with the upward-sloping supply curve. Equilibrium sits where the two cross, so price is set jointly — demand alone never fixes it. A frequent error is calling a luxury “inferior” — inferior goods have demand falling as income rises (a leftward shift), the reverse of normal goods. Memory hook: own price = along, anything else = shift.

Exam items almost always force the “movement along vs. shift” decision: a change in the good’s own price moves you along a fixed supply curve (a change in quantity supplied), whereas a change in input prices, technology, the number of sellers, producer expectations, or prices of related goods in production shifts the whole curve. The classic tell is a vignette naming a non-price cause — read for it, then pick “shift,” not “movement.” Watch the direction trap: a fall in input cost or a productivity gain shifts supply right (more at every price), which by itself pushes equilibrium price down.

Don’t confuse supply with demand: their determinants are different lists, and supply slopes upward while demand slopes downward, so they answer opposite shift questions. Also separate a single-curve shift from equilibrium analysis — the exam may shift supply only and ask for the new price/quantity, where supply rises but demand stays put. Memory hook: supply Sells, demand Demands — sellers want high prices, so supply rises with price.

Demand-pull inflation comes from spending growth outpacing supply; cost-push inflation comes from rising input costs (e.g., oil shocks). Real returns equal nominal returns less inflation — the Fisher relation. Inflation erodes the real value of fixed-rate bond cash flows but typically leaves equity claims on real assets relatively protected over long horizons.

The exam loves the sector-rotation question: given a phase of the cycle, pick which holdings to overweight. The “tell” is the verb — in a contraction you rotate toward defensive/non-cyclical names and away from high-beta cyclicals, the mirror image of an early expansion. A second favorite makes you sort lagging indicators (unemployment, CPI/inflation) from leading ones (yield-curve slope, building permits, manufacturers’ new orders) — the leading set turns before output does. Watch the trap that an inverted yield curve signals recession risk: it is a leading indicator with a long, variable lead, not proof a contraction has begun.

Do not confuse a recession (falling output) with deflation (falling prices) — link to inflation: in a demand-driven slump they often coincide as spending collapses, but stagflation shows recession with rising prices, breaking the reflex. Another classic trap: a demand-driven recession is a leftward shift in aggregate demand, not a movement along one good’s demand curve. Memory hook: defensives are your umbrella — you want utilities, staples, and healthcare when it rains.

The exam rarely asks you to define equilibrium — it tests the direction of adjustment. Expect a curve-shift vignette: a non-price determinant moves demand or supply (a change in own price is only a movement along a curve), and you predict the new equilibrium price and quantity. The “tell” is whether one curve shifts or both. With one shift, both move in a determinate direction; when both shift, one of price or quantity is indeterminate without the relative magnitudes — that ambiguity is usually the answer. Stability is the other favorite: equilibrium is stable when supply cuts demand from above (the usual upward-sloping supply). It turns unstable only in the odd case where supply cuts from below — a backward-bending supply flatter than a steep demand — so price diverges instead of converging.

Watch the shift vs. movement trap; the demand and supply pages hinge on it. Memory hook: “ceiling caps price low → shortage; floor props price high → surplus,” and a non-binding control does nothing.

The classic item shows a small-country import market and asks you to label the welfare areas after a tariff. The “tell” is that a small country is a price-taker, so the domestic price rises by the full tariff (world price plus the tariff). Drill the two deadweight-loss triangles: a production-efficiency loss (higher-cost domestic output replaces cheaper imports) and a consumption-efficiency loss (buyers priced out). The trap is the government-revenue rectangle — it’s the tariff times the post-tariff (reduced) import quantity, not pre-tariff imports, and it’s a transfer, not a loss. A large country can improve its terms of trade, so its net effect is ambiguous; small-country tariffs are unambiguously welfare-reducing.

Distinguish a tariff from a quota: a tariff hands the rectangle to the government, whereas an equivalent quota lets foreign exporters or license-holders capture the quota rents (the government gains only if it auctions the licenses). Don’t confuse this lost consumer surplus with the surplus/shortage disequilibrium of a binding price floor or ceiling — a different concept. Memory hook: tariffs tax, quotas quantity-cap.

Natural monopolies arise when economies of scale are so large that a single firm can supply the market at lower cost than several could. Government responses include regulation (price caps tied to cost of service), public ownership, or antitrust action. Monopoly creates deadweight loss because the monopolist restricts output below the competitive level.

The exam loves to make you match a model to an outcome. The tell is a phrase like “firms set output simultaneously” (Cournot), “identical products, price-cutting to marginal cost” (Bertrand → the zero-profit “Bertrand paradox,” broken by differentiation or capacity limits), or “a firm fears matched price cuts” (kinked demand → sticky prices from a gap in the marginal-revenue curve). A second favorite asks who has the most pricing power: rank it perfect competition < monopolistic competition < oligopoly < monopoly, and note a dominant oligopolist’s pricing depends on its market share and how elastic its buyers are.

The classic trap is conflating oligopoly with monopoly: both can earn economic profit, but oligopoly’s defining feature is interdependence, not a single seller. And separate the kinked-demand model (explains why prices are sticky, not how the level got set) from collusion/cartels (explains the price level). Hook: “few firms, watching each other” — Cournot watches quantities, Bertrand watches prices.

Expect a vignette giving two prices and two quantities, then asking you to compute own-price elasticity and read off the total-revenue effect. The tell is the sign trap: own-price elasticity is negative, so item-writers classify by absolute value — “elastic” means |E| > 1. Use the midpoint (arc) formula — percentage changes taken over the averages of the two prices and quantities — when two distinct points are given; the point formula (reciprocal of slope times P/Q) for one point on a linear curve. On a straight-line demand curve, elasticity is not constant: elastic up top, unit-elastic at the midpoint, inelastic at the bottom — so total revenue is maximized at the unit-elastic midpoint.

The classic error is confusing a movement along demand (an own-price change, which elasticity measures) with a shift from the other determinants — exactly the distinction the demand and supply cards draw. Don’t blur the families either: income elasticity classifies normal versus inferior, cross-price classifies substitutes versus complements, own-price drives revenue. Memory hook: cross-price substitutes = positive, complements = negative.

Economics items rarely ask for the definition; they hand you a graph or a policy and ask which area moved where. The reliable tell is a wedge driven between buyers and sellers — a price ceiling, floor, tax, quota, or tariff — and the answer hinges on tracking transfers versus losses. With a tariff, the higher domestic price raises producer surplus, generates government revenue on the imports that still flow, but cuts consumer surplus by more; the two triangles consumers lose that nobody else captures are the deadweight loss (a production-inefficiency triangle plus a lost-consumption triangle). Memorize that any intervention away from competitive equilibrium can only shrink total surplus, never grow it.

The classic trap is conflating the micro surpluses (consumer/producer, measured as areas) with the macro surpluses (trade, fiscal, current-account) — same word, unrelated accounting. A second trap: under a binding price ceiling, consumer surplus usually rises but the change is ambiguous — it can fall when demand is inelastic and the ceiling bites hard. Transfers reshuffle surplus; deadweight loss destroys it.