微观经济学第3讲.pdf

Utility Function Jin Xu HUST April 2013 Jin (HUST) April 2013 1 / 35 Review of Last Lecture Supply and Demand Model Qd = a + bP Qs = c dP Equilibrium Q (a, b, c , d ) =?; P (a, b, c , d ) =? Graphic Presentation Comparative Statics Analysis. example:∂ Q =? ∂a ∆ Qd Qd ∂ Qd P Elasticity of demand j j ∆P ∂ P Qd P Budget Constraint budget set= f(x ,x ) : p x + p x m,x 0,x 0g 1 2 1 1 2 2 1 2 How does tax a§ect budget line? Jin (HUST) April 2013 2 / 35 Review of Last Lecture (contíd) Preferences Three relations: % weakly preferred; strictly preferred; indi§erent Assumptions about Preferences Complete: For any consumption bundle x and y, either x % y or y % x Reáexive: x % x Transitive: If x % y and y % z ,then x % z Indi§erence Curve: IC (x ) = fy : y x g Well-behaved Preference Monotonicity: The more, the better If that x1 y1 ,x2 y2 and that x1 y1 ,x2 y2 at least one hold, then (x1 ,x2 ) (y1 ,y2 ). (!Indi§erence Curve is negatively sloped) Convexity: Averages are preferred to extremes. If (x1 ,x2 ) (y1 ,y2 ), then the bundle ( 1 x1 + 1 y1 , 1 x1 + 1 y1 ) % (x1 ,x2 ) and