偏好课件白底黑字.pdf

Chapter Three Preferences 偏好 Road Map • Describe preferences • Indifference curves (无差异曲线) • Well-behaved preferences • Marginal rate of substitution (边际替代率) Rationality in Economics • Behavioral Postulate: A decision-maker always chooses its most preferred alternative from its set of available alternatives. • So to model choice we must model decision-makers’ preferences. Preference Relations • Comparing two different consumption bundles, x and y: – strict preference (严格偏好): x is more preferred than is y (x y). π – Indifference (无差异): x is exactly as preferred as is y (x~y). – weak preference (弱偏好): x is as at least as preferred as is y (x y). φ ~ Preference Relations • Preference relations are ordinal relations; i.e. they state only the order in which bundles are preferred. Preference Relations • x y and y x imply x ∼y. φ φ ~ ~ Preference Relations • x y and y x imply x ∼y. φ φ ~ ~ π • x y and (not y x) imply x y. φ φ ~ ~ Assumptions about Preference Relations • Completeness (完备性): For any two bundles x and y it is always possible to make the statement that either x φy ~ or