《微观经济学》清华大学课件 Ch7 Revealed Preference显现性偏好

《微观经济学》清华大学课件

Chapter SevenRevealed Preference 显现性偏好

《微观经济学》清华大学课件

What Is the Question of the Chapter?

Suppose we observe a collection of a consumer’s choices, can we discover his/her preference? this possible at all? If so, under what conditions is this possible?

Is

(This is the reverse question of finding the optimal choice)

《微观经济学》清华大学课件

Digression: Science vs. Engineering (对比科学家思维与工程师思维) 找问题与解问题的不同 –要对问题提问题 务虚与务实的不同 解释世界与改造世界的不同 –旁观者与参与者的不同

《微观经济学》清华大学课件

Maintained Assumptions on Preferences Preferences

– do not change while the choice data are gathered. – are strictly convex. – are monotonic.

《微观经济学》清华大学课件

Assumptions on Preferencesx2

x2*

If preferences are convex and monotonic (i.e. well-behaved) then the most preferred affordable bundle is unique.

x1*

x1

《微观经济学》清华大学课件

Direct Preference Revelation Suppose

that the bundle x* is chosen when the bundle y is affordable. Then x* is revealed directly as preferred to y (otherwise y would have been chosen).

《微观经济学》清华大学课件

Direct Preference Revelationx2

The chosen bundle x* is revealed directly as preferred to the bundles y and z.x* z x1

y

《微观经济学》清华大学课件

Direct Preference Revelation That

x is revealed directly as preferred to y will be written as x

pD

y.

《微观经济学》清华大学课件

Indirect Preference Revelation Suppose

x is revealed directly preferred to y, and y is revealed directly preferred to z. Then, we call x is revealed indirectly as preferred to z. Write this as x z so xD

y and y

D

z

x

pI

p

pI

p

z.

《微观经济学》清华大学课件

Indirect Preference Revelationx2

z is not affordable when x* is chosen. x* is not affordable when y* is chosen. So x* and z cannot be compared x* directly. But x*x* y* y* D z and y* zx1

so x*

pI

p pD

z.

《微观经济学》清华大学课件

Two Axioms of Revealed Preference To

apply revealed preference analysis, choices must satisfy two criteria -- the Weak and the Strong Axioms of Revealed Preference.

《微观经济学》清华大学课件

The Weak Axiom of Revealed Preference (WARP) If

the bundle x is revealed directly as preferred to the bundle y then it is never the case that y is revealed directly as preferred to x; i.e.xD

y

not (y

pD

p

x).

《微观经济学》清华大学课件

The Weak Axiom of Revealed Preference (WARP) Choice

data which violate the WARP are inconsistent with economic rationality. The WARP is a necessary condition for applying economic rationality to explain observed choices.

《微观经济学》清华大学课件

The Weak Axiom of Revealed Preference (WARP) What

choice data violate the WARP?

《微观经济学》清华大学课件

The Weak Axiom of Revealed Preference (WARP)x2

x is chosen when y is available so x y.y is chosen when x is available so y x. y

xx1

pD

pD

《微观经济学》清华大学课件

Checking if Data Violate the WARP A

consumer makes the following choices: – At prices (p1,p2)=($2,$2) the choice was (x1,x2) = (10,1). – At (p1,p2)=($2,$1) the choice was (x1,x2) = (5,5). – At (p1,p2)=($1,$2) the choice was (x1,x2) = (5,4). Is the WARP violated by these data?