Kerala Plus Two Economics (DHSE) common mistakes
Kerala Plus Two Economics (DHSE) · Understand the traps and how to avoid them.
Writing that scarcity means a shortage of goods, or that scarcity disappears once an economy becomes rich, instead of defining it as limited resources relative to unlimited wants and linking it to the need for choice and opportunity cost.
Everyday use of the word 'scarce' means 'hard to buy', so candidates carry that meaning into the exam and lose the definitional mark; they also confuse scarcity (universal) with a shortage (a temporary market condition at a given price).
What to do instead
Practise writing the definition in one sentence with all three elements: unlimited wants, limited resources, therefore choice. Then immediately add the consequence chain: choice → opportunity cost → the central problems of what, how and for whom to produce. Test yourself by explaining why even a rich economy faces scarcity.
Treating total utility and marginal utility as interchangeable, or claiming a consumer is in equilibrium when marginal utility is highest rather than when marginal utility per rupee is equal across goods.
The two curves peak at different quantities, and candidates memorise 'MU = 0 means maximum satisfaction' without connecting it to total utility being maximised; the law of equi-marginal utility is then applied as MU alone rather than MU divided by price.
What to do instead
Draw the TU and MU schedules side by side for two goods and mark three points: where MU is highest, where MU = 0 (TU maximum), and where MU turns negative (TU falling). Then state the equilibrium condition in full: MUx/Px = MUy/Py, with the rupee-per-rupee comparison made explicit in the answer.
Describing a movement along the demand curve and a shift of the demand curve as the same thing, so a change in the good's own price is written as a 'decrease in demand'.
Both cases produce a leftward or downward movement on the diagram, and candidates match the picture rather than the cause; textbooks use 'change in quantity demanded' and 'change in demand' with only one word of difference.
What to do instead
Adopt a fixed two-column habit: own price → movement along the curve (expansion/contraction); any other determinant (income, prices of related goods, tastes, expectations, number of buyers) → shift (increase/decrease). In every answer name the determinant first, then say 'movement along' or 'shift' before drawing.
Confusing the short-run and long-run cost curves by drawing U-shaped AFC, or asserting that the long-run average cost curve is the envelope of the SAC curves at their minimum points.
The U-shape of AVC, ATC and MC is drilled in, so AFC's steadily falling rectangular hyperbola is forgotten; and the envelope relation is taught loosely, so candidates place the tangency at each SAC minimum rather than at the SAC minimum only for the plant that is optimal at that output.
What to do instead
Memorise the shape logic: AFC falls throughout because fixed cost is spread over more units; AVC and ATC are U-shaped because of the law of variable proportions; MC cuts both at their minimum. For the long run, draw the envelope and mark that tangency is at the SAC minimum only at the single point where the LAC itself is at its minimum.
Stating that a perfectly competitive firm maximises profit where price equals average cost, or shutting down whenever price falls below average total cost.
Candidates mix the profit-maximisation condition with the zero-economic-profit condition of long-run equilibrium, and they forget that in the short run a firm keeps producing while price covers average variable cost even if it does not cover average total cost.
What to do instead
Write the decision rule as a two-step test: (1) produce where MR = MC and MC is rising; (2) continue only if P ≥ minimum AVC, otherwise shut down. Under perfect competition MR = P, so the rule becomes P = MC. Draw the three zones - profit, loss-but-produce, shutdown - on one diagram and label the shutdown point at minimum AVC.
Assuming a monopolist charges the highest possible price, or that monopoly equilibrium is found where price equals marginal cost as under perfect competition.
The word 'monopoly' suggests unlimited pricing power, so candidates pick the top of the demand curve; and the P = MC habit from perfect competition is applied without noticing that under monopoly MR lies below AR, so the equilibrium condition is MR = MC and price is read off the demand curve above that quantity.
What to do instead
Always solve in the order: MR = MC gives quantity; go vertically to the demand curve to read price; then compare with the competitive outcome to show the higher price and lower output. Add the point that the monopolist still respects demand - it cannot sell more without lowering price - so 'highest price' is wrong.
Adding transfer payments, second-hand sales, intermediate goods or purely financial transactions into national income, or double-counting the value of output instead of using value added.
These items look like income to the person receiving them, and the distinction between a transfer and a factor payment is abstract; the value-added idea is also skipped because adding up final expenditure feels more natural.
What to do instead
Keep a rejection list with a one-line reason for each: pensions and scholarships are transfers (no production), second-hand sales are not current production, intermediate goods are already inside final value, shares and bonds are financial claims. Then practise the three methods (product, income, expenditure) on the same small economy to see they must agree.
Treating the money multiplier as the inverse of the reserve ratio without checking which deposits count, or claiming the central bank controls the money supply directly and completely.
The formula 1/RR is memorised as a mechanical rule, so candidates apply it to total deposits when only a new injection should be multiplied; and the role of commercial bank lending in creating deposits is understated, leading to an exaggerated claim of complete central bank control.
What to do instead
Work the process step by step on a single fresh deposit: new deposit, reserve kept, loan made, redeposit, and sum the geometric series to derive 1/RR. Then list the limits on central bank control - currency held by the public, excess reserves, and banks' willingness to lend - so the answer is qualified rather than absolute.
Confusing the government budget's revenue deficit with its fiscal deficit, or writing that a fiscal deficit is always inflationary and therefore bad.
Both deficits are defined by subtraction and differ only in whether borrowing is included; candidates memorise the formulas without the meaning. The normative claim comes from editorial reading rather than from the definition of deficit financing.
What to do instead
Anchor each deficit to one sentence: revenue deficit = revenue expenditure minus revenue receipts (borrowing to meet consumption); fiscal deficit = total expenditure minus total receipts excluding borrowings (total borrowing requirement); primary deficit = fiscal deficit minus interest payments. Then give both sides of the inflation argument, noting that the effect depends on whether the borrowing is from the central bank or the public.
Reading a rise in the exchange rate as an appreciation without checking which currency is being quoted, or treating a current account deficit as proof that the economy is badly run.
In India the exchange rate is often quoted as rupees per dollar, so a rise in that number is a depreciation of the rupee, but candidates apply the general 'rise means appreciation' rule; and the balance of payments is moralised rather than read as a set of accounting identities.
What to do instead
Before answering, write down the quotation convention in words ('rupees per dollar') and translate the movement into plain language ('the rupee now buys fewer dollars, so it has depreciated'). For the current account, separate the trade balance from invisibles and explain that a deficit is financed by a capital account surplus, so the question is about sustainability, not virtue.