300 likes | 1.05k Vues
Chapter 7 REVEALED PREFERENCE. 7.1 The Idea of Revealed Preference. ( x 1 , x 2 ) is chosen when ( y 1 , y 2 ) could have been chosen: p 1 x 1 + p 2 x 2 ≥ p 1 y 1 + p 2 y 2 ( x 1 , x 2 ) is directly revealed preferred to ( y 1 , y 2 ). 7.2 From Revealed Preference to Preference.
E N D
7.1 The Idea of Revealed Preference • (x1, x2) is chosen when (y1, y2) could have been chosen: p1x1+p2x2≥p1y1+p2y2 • (x1, x2) is directly revealed preferred to (y1, y2).
7.2 From Revealed Preference to Preference • The Principle of Revealed Preference • Suppose there is a unique optimal bundle for each budget set; • Suppose the consumer always chooses the most preferred bundle she can afford; • Suppose the consumer has chosen (x1, x2) when faced by (p1, p2); • Suppose p1x1+p2x2≥p1y1+p2y2; • we must have
7.2 From Revealed Preference to Preference • Suppose the consumer has chosen (y1, y2) when faced by (q1, q2); • Suppose q1y1+q2y2≥q1z1+q2z2; • Then we know that • From transitivity we can conclude that: • (x1, x2) is indirectly revealed preferred to (z1, z2).
7.2 From Revealed Preference to Preference • (x1, x2) is indirectly revealed preferred to (z1, z2).
7.3 Recovering Preferences • Suppose the preference is convex and monotonic. • The weakly preferred set w/r to X contains the “smallest” monotonic convex set that includes X, Y, and Z.
7.4 The Weak Axiom of Revealed Preference • WARP: If • (x1, x2) is directly revealed preferred to (y1, y2); • and (x1, x2)≠(y1, y2); • then (y1, y2) cannot be directly revealed preferred to (x1, x2).
7.4 The Weak Axiom of Revealed Preference • Satisfying WARP
7.6 The Strong Axiom of Revealed Preference • SARP: If • (x1, x2) is (directly or indirectly) revealed preferred to (y1, y2); • and (y1, y2)≠(x1, x2); • then (y1, y2) cannot be (directly or indirectly) revealed preferred to (x1, x2). • SARP is both necessary and sufficient for rational consumer behavior.
7.7 How to Check SARP • Transform the table: • Need to look for chains of arbitrary length to see if one observation is indirectly revealed preferred to another.
7.8 Index Numbers • Quantity index: • Paasche quantity index: • Laspeyres quantity index:
7.8 Index Numbers • The consumer is better off at t than at b. • No inference on consumer well-being.
7.8 Index Numbers • No inference on consumer well-being. • The consumer is better off at b than at t.
7.9 Price Indices • Price index: • Paasche price index: • Laspeyres price index:
7.9 Price Indices • The consumer is better off at b than at t. • The consumer is better off at t than at b.
Indexing Social Security Payments • Indexing: Social security payments get adjusted with price indices so that the consumption bundle in year b is still affordable in year t. • Consumers are strictly better off with indexing.