戰昇的部落格

以下是Week 10的課程內容摘要與心得，今天的講義是Market, perfect competition 和 monopoly。我認為算是比較難且需要開始記憶的內容了，以下是這禮拜的重點。

一、完全競爭市場 (Perfect Competition)

1. 完全競爭市場的假設

- 無限多的買家與賣家。

- 資訊完全透明，產品同質化，並且市場中有自由進出。

2. 短期與長期均衡

- 短期：固定資本，廠商數量固定，所有廠商技術相同。

- 長期：資本可調整，自由進出，利潤趨近於零，所有廠商達到最低有效規模 (MES)。

3. 社會福利

- 完全競爭市場中，社會福利最大化，消費者剩餘與生產者剩餘共同構成。

二、壟斷市場 (Monopoly)

1. 壟斷的特徵

- 只有一個生產者控制市場，無法進入的新進者，以及無可取代的產品。

2. 壟斷的價格設定

- 壟斷者依據市場需求曲線設置價格與產量，藉由價格大於邊際成本的方式獲取利潤。

3. 市場力量的影響

- 轉移消費者剩餘為壟斷利潤，並造成無謂損失 (Deadweight Loss)，損害整體社會福利。

4. 市場力量的衡量

- 使用價格加成率 (Markup) 或勒納指數 (Lerner Index) 測量壟斷市場力量。

心得總結

這週的課程讓我清楚理解了不同市場結構的特徵與其對社會福利的影響。特別是在壟斷市場中，企業如何透過減少產量來提高價格、提取消費者剩餘並造成無謂損失，這對經濟效率的損害令人印象深刻。

此外，完全競爭市場提供了一個理想化的基準，用來衡量其他市場結構中社會福利的減損。這週的課程也讓我對政府如何透過反壟斷法規 (如《謝爾曼法案》) 來限制壟斷力量有了更多的了解，期待能在未來課程中進一步學習相關政策的細節與應用。

Below is the summary and reflection for Week 10. Today’s lecture covered Market, Perfect Competition, and Monopoly. I found the content to be relatively challenging and requiring memorization. Here are the key points from this week:

A. Perfect Competition

1. Assumptions of Perfect Competition

- An infinite number of buyers and sellers.

- Complete transparency of information, homogeneous products, and free market entry and exit.

2. Short-Run and Long-Run Equilibrium

- Short-Run: Capital is fixed, the number of firms is fixed, and all firms have identical technologies.

- Long-Run: Capital can be adjusted, free market entry and exit occur, and profits approach zero as firms reach the Minimum Efficient Scale (MES).

3. Social Welfare

- In a perfectly competitive market, social welfare is maximized, consisting of both consumer surplus and producer surplus.

B. Monopoly

1. Characteristics of a Monopoly

- A single producer controls the market, with no new entrants and irreplaceable products.

2. Pricing in Monopoly

- A monopolist sets price and output based on the market demand curve, earning profits by setting prices above marginal cost.

3. Impact of Market Power

- Transfers consumer surplus into monopoly profits and creates deadweight loss, harming overall social welfare.

4. Measuring Market Power

- Market power is measured using the **Markup** or **Lerner Index**.

Reflection Summary

This week’s lecture gave me a clear understanding of the characteristics of different market structures and their impact on social welfare. In particular, it was striking to see how monopolists reduce output to raise prices, extracting consumer surplus and creating deadweight loss, which damages economic efficiency.

Additionally, the perfectly competitive market serves as an ideal benchmark to evaluate welfare losses in other market structures. This week’s content also deepened my understanding of how governments, through antitrust laws (e.g., the Sherman Act), regulate monopolistic power. I look forward to learning more about the details and applications of such policies in future lectures.