Chap 4 Consumers in Marketplace¶

from https://www.notion.so/Chap-4-Consumers-in-Marketplace-17ac94e393db45709d26c55bedebeb1b

Marginal Willingness to Pay¶

x = 商品數量 ; y = 其他 ; I = 所得

Px x + y = I

Marginal Willingness to Pay

MRS = |dx/dy| = Px/1

graph of quantity to income for a good (consists of tangent points at each income) 注意 x 軸是 P，y 軸是 Q 函數形式: Q(I) e.g. Qx = I/3 (103上期中 2.)

微分!!!

若函數是過原點直線， elasticity 一定為 1 (因為按比例)

I 對 Q 微分

P 對 Q 微分

\[\dfrac{\dfrac{\Delta Q_x}{Q_x}}{\dfrac{\Delta P_y}{P_y}}\]

the cross elasticity of demand for X with respect to Y = the percent change in consumption of X divided by the percent change in the price of Y

if positive → X & Y are substitutes if negative → X & Y are complements

判斷 normal, inferior, Giffen goods

wage 上升時，前者 income 上升較多，對 leisure hours 需求上升較多，working hours 淨上升量因此較少 supply curve 畫起來較陡

凹向下的 indifference curve 的 compensated demand curve (如果凹向下的 indifference curve 的 ordinary demand curve 是凹向下的話)

固定一點 P1 畫出其他價格用 sub effect 會切到的點發現價格很小時，P 上升一點，X 就上升很多價格愈來愈高時，與 P1 的 X 的差值的上升幅度就愈來愈小簡而言之設 P1 ~ P4 是等加數列 X4 - X1 < 3(X2 - X1) 畫出來就變右圖

很多錯看上面題目就好

作業題目

個經作業, Ch.4 1. Landsburg, Ch.4, numerical exercises, #N1. 2. Landsburg, Ch.4, problem set, #23. 3. Landsburg, Ch.4, problem set, #24. 4. In 2003, tolls were raised on seven bridges across the Delaware River, connecting Pennsylvania to New Jersey. In the first two months of the year, bridge traffic fell by 17%, but revenue increased by 123% because of the higher tolls. What is the price elasticity of demand for using these bridges to cross the Delaware River? (A problem from the previous edition.)