Economics Knowledge and Understanding
What you must know cold
This domain rewards precise command of core models and the language that surrounds them. Be able to define and apply: scarcity and opportunity cost; the production possibility frontier and its shifts; demand and supply determinants (distinguish a movement along a curve from a shift); equilibrium and the effects of price ceilings, price floors and indirect taxes; elasticity (price, income, cross) and its link to revenue; market failure including negative and positive externalities, public goods and common resources; and the macroeconomic aggregates - GDP, inflation, unemployment and the business cycle - plus the policy tools of fiscal and monetary policy and their transmission.
Traps that appear in questions
- Confusing a change in quantity demanded with a change in demand. Only price moves you along the curve; income, tastes, prices of substitutes/complements and expectations shift it.
- Treating GDP as a measure of welfare. It omits non-market activity, income distribution and environmental costs.
- Mixing up cost-push and demand-pull inflation, then recommending the wrong policy response.
- Forgetting that a price floor above equilibrium creates a surplus, while a ceiling below equilibrium creates a shortage.
- Describing expansionary fiscal policy as raising taxes.
Rule of thumb
Always state the mechanism in three steps: shock → curve or aggregate affected → new equilibrium and consequence. For example, a subsidy to producers shifts supply right, lowering price and raising quantity, which increases consumer surplus but imposes a budgetary cost.
Worked example
A government sets a minimum wage above the market-clearing wage. Step one: the wage is a price floor. Step two: quantity of labour supplied rises while quantity demanded falls. Step three: a surplus of labour - unemployment - emerges, concentrated among low-skilled workers. A strong answer also notes that if the floor is set below equilibrium it is non-binding and has no effect.