北京大学：《微观经济学》Chapter Three Preferences 偏好

Chapter Three Preferences 偏好

Chapter Three Preferences 偏好

Structure Describe preferences difference curves(无差异曲线) Well-behaved preferences Marginal rate of substitution(边际替 代率)

Structure 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 decisionmaker always chooses its most preferred alternative from its set of available alternatives So to model choice we must model decision-makers'preferences

Rationality in Economics Behavioral Postulate: A decisionmaker 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):xis more preferred than is y(x>y - difference(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)

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). – 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). p ~ f

Preference relations Preference relations are ordinal relations; i.e. they state only the order in which bundles are preferred

Preference Relations Preference relations are ordinal relations; i.e. they state only the order in which bundles are preferred

Preference relations x y andy x imply xy

Preference Relations x y and y x imply x ~ y. ~ f ~ f

Preference relations x y andy x imply xy X y and(not y x)imply x>y

Preference Relations x y and y x imply x ~ y. x y and (not y x) imply x y. ~ f ~ f ~ f ~ f p

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 y or y∑x

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 y or y x. ~ f ~ f

Assumptions about Preference Relations Reflexivity(反身性): Any bundle x is always at least as preferred as itself 丿e X 7 X

Assumptions about Preference Relations Reflexivity (反身性): Any bundle x is always at least as preferred as itself; i.e. x x. ~ f

Assumptions about Preference Relations Transitivity(传递性):If x is at least as preferred as y, and y is at least as preferred as z, then x is at least as preferred as z; ie x y andy x

Assumptions about Preference Relations Transitivity (传递性): If x is at least as preferred as y, and y is at least as preferred as z, then x is at least as preferred as z; i.e. x y and y z x z. ~ f ~ f ~ f