戰昇的部落格

今天是 Week 6，課程內容涵蓋了 跨期選擇 (Intertemporal Choice)、不確定性 (Uncertainty) 和 福利分析 (Welfare Analysis)。以下分主題整理：

一、跨期選擇 (Intertemporal Choice)

1. 跨期分配與效用極大化

- 消費者需要在多個時期間分配收入，例如如何平衡當前消費與儲蓄。

- 理論基於終身預算限制，研究如何在不同時期間達到效用最大化。

2. 利率的角色

- 利率作為機會成本，影響消費者對當期與未來消費的選擇。

- 利率上升可能使借貸者變為貸款人，但影響取決於替代效果與所得效果的相對大小。

3. 最適消費計劃

- 消費者的偏好與利率結合，用於確定跨期消費流的最適配置。

二、不確定性 (Uncertainty)

1. 期望效用假說

- 消費者基於可能的狀態與其對應的效用，通過期望效用極大化進行選擇。

- 例如，購買保險來對抗火災等潛在風險，分配財富以降低不確定性帶來的影響。

2. 風險態度

- 風險趨避者 (Risk-averse)：偏好較低風險的選擇，期望效用小於確定財富的效用。

- 風險中立者 (Risk-neutral)：無差異於風險的存在。

- 風險愛好者 (Risk-lover)：偏好更高風險的選擇，期望效用大於確定財富的效用。

3. 應用：保險與財富再分配

- 透過購買保險合同，消費者在不同狀態間調整消費計劃以最大化滿意度。

 三、福利分析 (Welfare Analysis)

1. 消費者剩餘與福利變化

- 消費者剩餘 (Consumer Surplus) 量化市場交易中獲得的福利。

- 政策影響分析通過衡量效用變化來確定福利得失，使用補償變異 (Compensating Variation) 或等價變異 (Equivalent Variation) 表示。

2. 政策影響量化

- 補償變異 (CV)：衡量為維持原效用水平所需的額外收入，常用於不利政策影響的分析。

- 等價變異 (EV)：衡量消費者達到新效用水平所需的收入，適合分析有利政策影響。

3. 實例：Cobb-Douglas 效用函數

- 具體分析稅收政策對消費者選擇與福利的影響，量化福利損失或收益。

心得總結

我認為跨期選擇是蠻重要的，要學會分辨利率變化、貸款者以及借款者，都有不同的計算方式。

但是我認為最難的就是政策的影響量化，補償變異跟等價變異的公式常常都會忘記。

此外，這堂課讓我對經濟學中的實用工具有更深的理解，也讓我意識到政策分析不僅僅是數學計算，更需要深入的經濟洞察力來解讀結果。期待能在未來的課程中進一步掌握這些概念的應用。

Today is Week 6, and the lecture covered Intertemporal Choice, Uncertainty, and Welfare Analysis. Below is a breakdown by topic:

A. Intertemporal Choice

1. Intertemporal Allocation and Utility Maximization

- Consumers allocate their income across multiple periods, balancing current consumption and savings.

- The theory, based on lifetime budget constraints, examines how consumers maximize utility across different time periods.

2. Role of Interest Rates

- Interest rates act as an opportunity cost, influencing consumers' choices between current and future consumption.

- An increase in interest rates may turn borrowers into lenders, depending on the relative sizes of the substitution and income effects.

3. Optimal Consumption Plan

- Consumers’ preferences combined with interest rates determine the optimal allocation of consumption over time.

B. Uncertainty

1. Expected Utility Hypothesis

- Consumers make decisions by maximizing expected utility based on possible states and their associated utilities.

- For example, buying insurance to mitigate risks such as fire, reallocating wealth to reduce the impact of uncertainty.

2. Attitudes Toward Risk

- Risk-averse: Prefers lower-risk options; expected utility is less than the utility of certain wealth.

- Risk-neutral: Indifferent to the presence of risk.

- Risk-loving: Prefers higher-risk options; expected utility exceeds the utility of certain wealth.

3. Applications: Insurance and Wealth Redistribution

- By purchasing insurance policies, consumers adjust their consumption plans across different states to maximize satisfaction.

C. Welfare Analysis

1. Consumer Surplus and Welfare Changes

- Consumer surplus quantifies the welfare gained from market transactions.

- Policy impacts are analyzed by measuring changes in utility to determine welfare gains or losses, represented by **Compensating Variation (CV)** or **Equivalent Variation (EV)**.

2. Quantifying Policy Impacts

- Compensating Variation (CV): Measures the additional income needed to maintain the original utility level, often used for analyzing adverse policy impacts.

- Equivalent Variation (EV): Measures the income required for consumers to achieve the new utility level, suitable for analyzing favorable policy impacts.

3. Example: Cobb-Douglas Utility Function

- Analyzes the impact of tax policies on consumer choices and welfare, quantifying welfare losses or gains.

Reflection Summary

I believe intertemporal choice is very important, as it requires understanding the differences in calculations for interest rate changes, lenders, and borrowers.

However, I find quantifying policy impacts to be the most challenging aspect. The formulas for compensating variation (CV) and equivalent variation (EV) are often easy to forget.

Moreover, this lecture deepened my understanding of practical tools in economics and made me realize that policy analysis is not just about mathematical calculations but also requires deep economic insights to interpret the results. I look forward to further mastering the application of these concepts in future lessons.