戰昇的部落格

今天是第二個禮拜的課程，一次發了兩個講義，分別是講預算限制線以及偏好

一、預算限制（Budget Constraints）

1. 市場經濟與資源分配
   課程介紹市場經濟中，資源透過個人交易（如商品或服務交換）進行分配的方式，並與計畫經濟進行比較。  
   以日常例子（如牙膏分配）說明市場運作模式。

2. 預算集合與預算線 
   - 預算集合（Budget Set）是所有能負擔的消費組合，而預算線（Budget Line）則是耗盡收入的消費組合。  
 

3. 預算線的斜率與機會成本
   - 預算線斜率的絕對值代表「市場替代率」，即消費者購買額外單位商品1時，必須放棄多少單位商品2。  
 

4. 價格與收入變動的影響
   - 價格變動：如商品價格增加，預算線向內傾斜，減少可負擔的商品數量。  
   - 收入變動：收入增加會使預算線平行向外移動。  

5. 政策分析  
   - 稅收與補貼對預算線的影響：銷售稅導致預算線內傾，而補貼則使預算線外移。  

二、偏好（Preferences）

1. 偏好的基本公理  
   - 完備性：消費者能夠比較任意兩個組合的偏好（如偏好A於B，或兩者無差異）。  
   - 反身性：任何組合都至少與自己一樣令人滿意。  
   - 傳遞性：如果偏好A於B，且偏好B於C，則偏好A於C。

2. 無差異曲線（Indifference Curve） 
   - 定義：代表所有與某消費組合效用相同的組合集合。  
   - 性質：  
     - 曲線不相交。  
     - 曲線向下傾斜，且凸向原點。  

3. 邊際替代率（MRS）
   - 定義：維持相同滿意度時，增加單位商品1所需放棄的商品2數量。  
   - 邊際替代率會隨商品1的增加而遞減，說明消費者對商品1的額外需求降低。  

4. 偏好的應用與下一步
   - 課程結尾提出「效用函數」的概念，作為分析消費者選擇行為的工具。  

Today was the second week of the course, and we received two handouts: one on budget constraints and the other on preferences.

A. Budget Constraints

1. Market Economy and Resource Allocation

- The lecture introduced how resources are allocated in a market economy through individual transactions, such as the exchange of goods or services, and compared it with planned economies.

- Everyday examples, like toothpaste allocation, were used to illustrate how markets operate.

2. Budget Set and Budget Line

- The Budget Set represents all affordable consumption bundles, while the **Budget Line** consists of consumption bundles that exhaust income.

3. Slope of the Budget Line and Opportunity Cost

- The absolute value of the budget line’s slope represents the "market rate of substitution," indicating how many units of commodity 2 must be forgone to purchase an additional unit of commodity 1.

4. Effects of Price and Income Changes

- Price Changes: When the price of a commodity increases, the budget line tilts inward, reducing the number of affordable goods.

- Income Changes: An increase in income shifts the budget line outward in parallel.

5. Policy Analysis

- The effects of taxes and subsidies on the budget line: sales tax causes the budget line to tilt inward, while subsidies shift it outward.

B. Preferences

1. Axioms of Preferences

- Completeness: Consumers can compare any two bundles (e.g., preferring A to B or being indifferent).

- Reflexivity: Any bundle is at least as satisfactory as itself.

- Transitivity: If A is preferred to B, and B is preferred to C, then A is preferred to C.

2. Indifference Curves

- Definition: Represents all bundles that provide the same level of satisfaction as a particular consumption bundle.

- Properties:

- Indifference curves do not cross.

- They slope downward and are convex toward the origin.

3. Marginal Rate of Substitution (MRS)

- Definition: The amount of commodity 2 that must be given up to obtain an additional unit of commodity 1 while maintaining the same level of satisfaction.

- MRS diminishes as the quantity of commodity 1 increases, indicating reduced additional demand for commodity 1.

4. Applications of Preferences and the Next Step

- The lecture introduced the concept of the utility function, which serves as a tool to analyze consumer choice behavior.