ECO 06 Solved Guess Paper 2026 | IGNOU Economic Theory for B.Com, BA and BDP (Elective Commerce)

Consumer's surplus with diagram and limitations

Question: Explain the concept of consumer's surplus with the help of a diagram. What are its limitations?

Meaning of consumer's surplus

"The excess of the price which he (the consumer) would be willing to pay rather than go without the thing over that which he actually does pay is the economic measure of this surplus satisfaction. It may be called consumer's surplus."

In brief, consumer's surplus is the excess of what a consumer is ready to pay for a commodity over what he actually pays for it. It arises because every commodity obeys the law of diminishing marginal utility: the earlier, intra-marginal units give more utility than the price paid, while only the last unit's utility equals the price.

Diagrammatic explanation

Quantity is measured on the X-axis and price or marginal utility on the Y-axis. The consumer buys OM units at price PM and pays a total of OBPM. To obtain OM units, however, he was ready to pay OBDPM, the whole area under the demand curve. His consumer's surplus is therefore OBDPM minus OBPM, which is the shaded triangle BDP.

Limitations

1. It is difficult to measure exactly, since utility cannot be measured in precise cardinal units.
2. For related goods, substitutes or complements, the utility of one depends on the quantity of the other, which complicates measurement.
3. Extending the analysis from a single consumer to the whole market raises further problems.

Despite these limits, the idea has real practical value. Necessities yield a larger surplus, so authorities should tax luxuries and comforts rather than necessities.

Conclusion: Consumer's surplus, introduced by Marshall, measures the extra satisfaction a buyer enjoys beyond the price paid; though hard to measure, it guides taxation and pricing policy.

Forms of economic system and features of a mixed economy

Question: What are the various forms of economic system? Describe the features of a mixed economy.

Meaning of an economic system

"The mechanism that decides in a society as to what to produce, how to produce, how much to produce and for whom to produce is known as the economic system."

Forms of economic system

1. Capitalism: production and the means of production are privately owned and guided by the profit motive and the price mechanism.
2. Socialism: the means of production are socially or state owned, and economic activity is centrally planned.
3. Mixed economy: a variant of capitalism marked by the co-existence of public and private sectors.

Features of a mixed economy

1. Private ownership and profit-guided production: the right to property is guaranteed, and the private sector usually accounts for 70 to 90 per cent of gross output.
2. Decisive role of the market mechanism: markets exist for consumer goods, producer goods and factors of production, with prices set by demand and supply, though the State may regulate prices of essential commodities.
3. Public sector: it co-exists with the private sector and develops basic and heavy industries the private sector cannot, so its role is supplementary.
4. Economic planning: planning is adopted to speed up growth, relying more on economic incentives than on direction.

Conclusion: A mixed economy keeps the core institutions of capitalism while the government moderates their working through the public sector, planning and regulatory controls.

Oligopoly: meaning and characteristics

Question: What is oligopoly? Explain its characteristics.

Meaning of oligopoly

"Oligopoly is a form of market structure in which a few sellers sell differentiated or homogeneous products."

An oligopoly market is marked by a relatively small number of firms, difficult entry, and a product that is either standardised or differentiated. Each seller commands a sizeable share of the market.

Characteristics

1. Competition: with only a few sellers, any move by one immediately affects its rivals, so each firm keeps a close watch on the others.
2. Interdependence: a change in price or output by one firm provokes a reaction from the others. Interdependence in decision-making is the main characteristic of oligopoly.
3. Difficult entry: strong barriers such as economies of scale, price cuts and excess capacity keep new firms out.

Types of oligopoly

1. Discriminatory oligopoly: firms sell close substitutes with real or imaginary differences.
2. Pure oligopoly: all firms produce identical products with no product differentiation.

Conclusion: The defining feature of oligopoly is the recognised mutual interdependence of a few large sellers in the market.

Firm's short-period equilibrium under perfect competition

Question: Explain a firm's short period equilibrium under perfect competition.

Meaning

Under perfect competition there are a very large number of buyers and sellers and a homogeneous product, so the firm is a price-taker: price (P) equals average revenue (AR) and marginal revenue (MR). The firm chooses the output at which its profit is maximum. In the diagram, equilibrium is at E, where the rising MC curve cuts the horizontal P = AR = MR line.

Conditions of short-run equilibrium

1. Marginal cost equals marginal revenue (MC = MR) at a level of output from which no profitable variation is possible.
2. Beyond the MC = MR output, marginal cost must be greater than marginal revenue, which means the MC curve cuts MR from below.
3. Price, or AR, must be greater than or equal to average variable cost (AVC); otherwise the firm shuts down.

Possible outcomes

In the short run the firm in equilibrium may earn supernormal profits when AR is above AC, normal profits when AR equals AC, or minimise losses when AR covers AVC and part of fixed cost. If price falls below AVC, the firm stops production.

Conclusion: A competitive firm is in short-run equilibrium where MC = MR = price, with MC rising and price at least covering average variable cost.

Rent and quasi-rent distinguished

Question: Distinguish between Rent and Quasi-Rent.

Rent

"The essence of the conception of rent is the conception of a surplus earned by a particular part of a factor of production over and above the minimum earnings necessary to induce it to do its work."

Quasi-rent

Marshall first used the term quasi-rent in his Principles of Economics. Factors such as capital equipment can be inelastic in supply in the short period, so they earn a surplus over their supply price; Marshall called this surplus quasi-rent. Today it is defined as the surplus a producer gets in the short period over his variable costs.

Conclusion: Land earns rent because its supply is permanently fixed, whereas quasi-rent is only a short-period surplus that disappears in the long run as the supply of other factors increases.