EGEL Plus Economía common mistakes
EGEL Plus Economía · Understand the traps and how to avoid them.
Resolving microeconomics exercises (elasticity, consumer/producer surplus, market equilibrium) by memorizing formulas and plugging in numbers without first drawing or mentally mapping the supply-and-demand graph, then failing to notice when the answer requires interpreting a shift versus a movement along the curve.
Candidates drill formula sheets from preparatory courses and treat the exam as a calculation test, so they skip the graphical reasoning the item is actually testing; when the item presents a scenario in words (a price ceiling, a subsidy, an income change) they apply the wrong formula because they never identified which curve shifts.
What to do instead
Before computing, write one line: which curve shifts, which direction, and what happens to P* and Q*. Only then substitute numbers. Practice 20 items where the same elasticity formula is used under different scenarios (price change vs. income change vs. cross-price) and label each before solving.
Confusing the macroeconomic accounting identities and their components: mixing up GDP vs. GNP, nominal vs. real, the expenditure approach vs. the income approach, and treating transfers or intermediate goods as part of GDP.
These distinctions are taught early and revisited superficially, so under time pressure candidates default to the most familiar formula (C+I+G+X) and misclassify items such as government transfers, used-goods sales, or inventory changes.
What to do instead
Build a one-page classification table with columns: included in GDP / excluded, and why. Add explicit rules: transfers excluded, intermediate goods excluded, inventory investment included, net exports = X − M. Do 15 rapid classification drills before moving to numerical problems.
Reading a monetary-policy or fiscal-policy item and answering with the desired outcome (e.g., 'inflation falls') instead of the mechanism the item asks for (e.g., 'the central bank sells bonds, the money supply falls, the interest rate rises'), or reversing the direction of the transmission chain.
Candidates know the end goal of policy and pattern-match to it, skipping the intermediate steps; the exam deliberately tests the sequence, and reversed chains (open market purchase → rate falls) are the most common distractor.
What to do instead
Write the transmission chain as an explicit arrow sequence every time: instrument → money supply → interest rate → investment/consumption → aggregate demand → output/price level. Check the direction of each arrow separately; do not answer until the chain is complete.
Misapplying elasticity rules: treating inelastic demand as elastic, confusing price elasticity of demand with income or cross-price elasticity, or failing to connect elasticity to total revenue and tax incidence.
The absolute-value convention and the sign conventions differ across the three elasticities, and candidates memorize 'elastic = flat' without the revenue and incidence implications the exam tests.
What to do instead
Memorize the sign conventions explicitly (own-price negative, income positive for normal goods, cross-price positive for substitutes) and the revenue rule (price rise raises revenue only if demand is inelastic). Practice linking elasticity to who bears the tax burden: the more inelastic side bears more.
In cost-theory items, conflating short-run and long-run cost curves, mixing average and marginal concepts, or misidentifying the profit-maximizing condition (MR = MC) with the shutdown condition (P < AVC).
The vocabulary is dense and similar-sounding; candidates see 'average total cost' and 'marginal cost' in the same item and pick the wrong one, or forget that the firm shuts down only below average variable cost, not average total cost.
What to do instead
Draw the standard cost-curve diagram from memory (MC crossing ATC and AVC at their minima) and annotate the profit-maximizing point and the shutdown point. For each item, state in words which decision is being asked: how much to produce (MR = MC) or whether to produce at all (P vs. AVC).
Treating market structures as labels to memorize rather than as testable predictions: failing to derive why a perfectly competitive firm is a price taker, why a monopolist produces where MR = MC with P > MC, or what happens to deadweight loss under monopoly versus perfect competition.
Candidates learn the four structures as a list (competition, monopolistic competition, oligopoly, monopoly) and cannot apply the underlying assumptions (number of firms, product differentiation, barriers to entry) to a novel scenario.
What to do instead
Build a comparison matrix with rows for number of firms, entry barriers, product differentiation, price-setting power, long-run profit, and efficiency outcome. Then solve three items per structure that ask for a prediction rather than a definition.
In international economics items, confusing the effects of tariffs versus quotas, or misreading how exchange-rate movements affect the trade balance and which currency appreciates.
Both tariffs and quotas restrict imports, so candidates treat them as interchangeable and miss the quota's rent-creation and the tariff's revenue effect; exchange-rate direction is often reversed because the item is read quickly.
What to do instead
Write the tariff and quota effects side by side (price rise, quantity fall, government revenue vs. quota rents, deadweight loss). For exchange rates, always anchor to 'price of foreign currency in domestic currency' and state the direction in words before choosing an answer.
Skipping or rushing the quantitative section under time pressure: leaving calculation items blank, or producing arithmetic errors in percentage changes, index numbers, and growth rates because the formula is applied without checking units and base periods.
The exam is timed and quantitative items are perceived as slow, so candidates guess or abandon them; when they do attempt them, they mix up base-year conventions in index numbers and real vs. nominal growth.
What to do instead
Adopt a two-pass strategy: answer all conceptual items first, then return to calculations with remaining time. For each calculation, write the formula, the base period, and the units before substituting; verify percentage changes with the midpoint formula when the item specifies it.
Answering definitional items with a related but incorrect term (e.g., 'recession' for 'depression', 'deflation' for 'disinflation', 'budget deficit' for 'public debt', 'economic growth' for 'economic development'), because the terms are learned as a cluster without sharp boundaries.
Preparatory material groups these concepts in the same chapter, and candidates recognize the topic but not the precise discriminator the item is testing.
What to do instead
Maintain a 'confusable pairs' glossary with a one-line discriminator for each pair (disinflation = falling inflation rate, deflation = falling price level; deficit = annual flow, debt = accumulated stock). Review it weekly and self-test by writing the discriminator from memory.
Ignoring the item stem's qualifiers ('in the short run', 'ceteris paribus', 'assuming perfect competition', 'according to the Keynesian model') and answering from general intuition instead of the stated framework.
Candidates read the topic keywords and jump to a familiar answer, missing that the qualifier changes which model or time horizon applies; many items are built specifically around a qualifier that flips the correct answer.
What to do instead
Underline or mentally box every qualifier in the stem before looking at the options, and reject any option that contradicts a stated assumption even if it is true in general. Practice with paired items that differ only in their qualifier.