Q.Explain the consumer's equilibrium using indifference curve.

A consumer reaches equilibrium where the budget line just touches (is tangent to) the highest possible indifference curve. The two conditions are: (1) the necessary condition — slope of indifference curve = slope of budget line, i.e. MRSxy = Px/Py; and (2) the sufficient condition — the indifference curve must be convex to the origin at that point. ## Meaning of consumer's equilibrium A consumer is said to be in equilibrium when, given his money income and the market prices of goods, he buys that combination of goods which yields him the maximum possible satisfaction and he has no tendency to change it. ## The two tools used - Indifference curve (IC): a curve showing all combinations of two goods (say X and Y) that give the consumer the same level of satisfaction. A higher IC represents a higher level of satisfaction. ICs slope downward, are convex to the origin, and never intersect. - Budget line (price line): a line showing all combinations of the two goods the consumer can buy by spending his entire income at the given prices. Its slope equals the price ratio Px/Py. ## Assumptions - The consumer is rational and aims at maximum satisfaction. - Utility is ordinal (satisfaction is ranked, not measured in numbers). - Income of the consumer and prices of goods are given and constant. - The consumer has a scale of preferences and consistent choices. ## Conditions of equilibrium 1. Necessary (first-order) condition — tangency: The budget line must be tangent to an indifference curve. At the point of tangency the slope of the IC equals the slope of the budget line: Marginal Rate of Substitution (MRSxy) = Px / Py The MRS is the rate at which the consumer is willing to give up Y for an extra unit of X, while the price ratio is the rate at which the market allows him to exchange them. Equilibrium is reached only when the two are equal. 2. Sufficient (second-order) condition — convexity: At the point of tangency the indifference curve must be convex to the origin, i.e. MRS must be falling. This ensures the point is one of maximum (not minimum) satisfaction. ## Explanation with the diagram Suppose the budget line is AB and the consumer faces indifference curves IC1, IC2 and IC3 (IC3 being the highest). The consumer cannot reach IC3 because it lies beyond his budget line AB. Points on IC1 (where AB cuts IC1 at two points) are attainable but give less satisfaction. The consumer moves to the point 'E' where the budget line AB is tangent to IC2 — the highest curve he can reach …