JAMB Economics 1990 Past Questions & Explanations

A firm minimizes costs by substituting factors of production until the ratio of their marginal physical products (MPP) equals the ratio of their prices. This is the condition for least-cost factor combination: $\frac{MPP_L}{MPP_K} = \frac{P_L}{P_K}$. Option A is incorrect because factor prices may differ based on their productivity. Option C confuses marginal physical product with factor price. Option D describes zero productivity, which is economically irrelevant for optimization.

Economies of scale occur when average cost (AC) falls as output increases. This reflects the firm's ability to produce larger quantities at lower per-unit costs due to spreading fixed costs and operational efficiencies. Option A describes marginal cost behavior, which is related but not definitive. Option C is nonsensical—fixed costs cannot become variable by definition. Option D describes a cost structure but doesn't define economies of scale.

At profit maximization, the firm produces where marginal revenue (MR) equals marginal cost (MC). At this equilibrium point, MC must be rising because if MC were falling, the firm could expand output further and increase profit. When MC is rising and intersects MR, this represents the optimal output level. The firm stops expanding before MC reaches its minimum to maximize profit.

Constant returns to scale occurs when a proportional increase in all inputs leads to the same proportional increase in output. If doubling inputs results in double output, the firm is experiencing constant returns to scale. Option A refers to the ratio of inputs used. Option B is incomplete terminology. Option C describes increasing returns where output grows more than proportionally to input increases.

The law of diminishing marginal utility states that as consumption of a good increases, the satisfaction (marginal utility) gained from each additional unit decreases. While total utility typically continues to rise (until it peaks), marginal utility—the additional satisfaction from one more unit—must decline. Option A is incorrect because total utility usually continues rising. Option C contradicts the law's core premise. Option D is impossible because when MU falls while remaining positive, total utility still rises.

Technical progress reduces production costs, shifting the supply curve rightward. With increased supply at each price level, equilibrium moves along the demand curve: price decreases and quantity increases. This reflects the economic benefit of technological improvement—lower costs enable lower prices while producers sell more units. Options A and C would result from leftward supply shifts (negative shocks). Option B is inconsistent with supply-side improvements.

An inferior good is one where demand decreases as consumer income rises. When income increases and consumption of beans falls, this indicates beans are inferior goods—typically lower-quality or budget items that consumers replace with better alternatives as they become wealthier. Option A describes normal goods where demand rises with income. Option C relates to goods that replace each other (cross-price elasticity). Option D is a special case of inferior goods with unusual demand behavior.

Price inelastic demand occurs when the price elasticity of demand (PED) is less than one ($|PED| < 1$). This means quantity demanded is relatively unresponsive to price changes. A percentage change in price causes a smaller percentage change in quantity demanded. Option B describes elastic demand where $|PED| > 1$. Options C and D describe normal demand behavior but don't define elasticity.

A monopsony is a market structure with a single buyer and many sellers. The buyer has significant power to influence prices and terms. This is the demand-side counterpart to monopoly (single seller). Option B (oligopoly) describes few sellers. Option C (monopoly) describes one seller, not one buyer. Option D (duopoly) describes two sellers.

Tailoring services form a competitive market because entry barriers are low and many small-scale, independent tailors operate. Each tailor has limited market power, and consumers can easily switch between providers. Large-scale enterprises would concentrate market power and reduce competition. Medium-scale and government enterprises don't characterize the tailoring industry, which is typically dominated by individual craftspeople and small shops.

In monopoly, at the point where $MC = MR$, the monopolist charges a price determined by the demand curve at that output level. Since the demand curve slopes downward and lies above the MR curve (which is below it), price is always above marginal revenue for a monopolist. Option A is incorrect because minimum cost occurs at minimum AC, not at MR = MC. Option B refers to long-run equilibrium conditions not guaranteed here. Option D is incorrect; AVC minimum doesn't coincide with profit-maximization.

Bulk breaking (or breaking bulk) is the primary function of wholesalers. They purchase large quantities from manufacturers and divide them into smaller quantities to sell to retailers. This bridges the gap between manufacturer production scales and retail consumption. Option B is secondary market research. Option C is primarily a retailer's function. Option D, while wholesalers provide warehousing, is not their major distinguishing function.

The middleman's mark-up margin (the difference between buying and selling price) represents the compensation for their business services—organizing distribution, managing inventory, providing market information, and bearing business risks. This is the economic reward for their entrepreneurial function in the distribution chain. Option A relates to pricing strategies, not mark-up meaning. Option C involves regulatory matters. Option D imposes a normative judgment not inherent in mark-up economics.

Manufacturers may bypass wholesalers to directly collect market information about their products' performance, consumer preferences, and retailer feedback. Direct distribution channels provide valuable data for product improvement and marketing strategy. Option A is a wholesaler's function, not a reason to bypass them. Option C describes warehousing, another wholesaler function. Option D involves illegal activity—no manufacturer would cite this as legitimate motivation.

State-owned enterprises serve public objectives (social welfare, universal service provision) and aren't always expected to maximize profits, whereas private enterprises prioritize profit maximization. Public enterprises may operate at losses to provide essential services. Option A is too extreme; public enterprises should generally cover costs. Option C is backwards—private companies have shareholders; state enterprises have public ownership. Option D is incorrect; both types typically have boards.

A limited liability company (LLC) separates ownership from control: shareholders own the company but professional managers control day-to-day operations. This separation is a key feature of corporate organization. In sole proprietorships, the owner controls the business directly. Partnerships have direct owner involvement in management. Private limited companies, while they can have separation, are not distinctively characterized by this feature compared to LLCs.

Equity capital is financing provided by investors through purchasing stocks (shares) in a company. These investors become part owners. Option A (debt capital) comes from loans or bonds—creditors, not owners. Option B (fixed capital) refers to long-term physical assets like machinery. Option C (circulating capital) is short-term working capital used in operations. Equity capital specifically denotes ownership financing.

For petrochemical plants, proximity to raw material sources (crude oil or petroleum refining facilities) is paramount because raw materials are bulky, costly to transport, and subject to significant weight loss in processing. Locating near supply reduces transportation costs dramatically. While power and labor are important, they are more flexible regarding location. Financial institutions have minimal location bearing on industrial siting.

When only economic factors (cost minimization, resource proximity, market access) determine industrial location, industries concentrate in already-developed regions with established infrastructure, lower costs, and larger markets. This creates unbalanced regional development with industrialized centers and underdeveloped peripheries. Option A describes the opposite outcome. Option C is incorrect because less developed regions lack the economic advantages attracting industry. Option D misses the point about economic determinants.

The price index is calculated as: $\text{Price Index} = \frac{\text{Price in Current Year}}{\text{Price in Base Year}} \times 100$. Using 1985 as the base year: $\text{Price Index}_{1987} = \frac{15.00}{12.00} \times 100 = 1.25 \times 100 = 125$. This indicates a 25% increase in prices from 1985 to 1987. Option A is incorrectly calculated. Option B represents a decline. Option C would indicate no change.