Model Thinking1

　　　　Why Model

Reason # 1: Intelligent Citizen of the World

Reason # 2: Clearer Thinker

Reason # 3: Understand and Use Data

Reason # 4: Decide, Strategize, and Design

•The model

–Assumptions, results, applications

•Technical Details

–Measures, Proofs (Easy, Medium, Hard)

–Practice Problems

•Fertility

 

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　　　　Intelligent Citizen of the World

Models Are Better Than We Are

Models Are Fertile【肥沃的;可繁殖的;丰富的;[物]能产生裂变物质的】

Models Make Us Humble

Many Model Thinkers Know Best

 

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　　　　Thinking More Clearly

Name The Parts

Identify Relationships

Work Through Logic

Inductively Explore

Understand Class of Outcome

　　　　Equilibrium【平衡，均势;平静】

　　　　Cycle

　　　　Random

　　　　Complex

Identify Logical Boundaries

Communicate

 

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　　　　Using and Understanding Data

Understand Patterns

Predict Point

Produce Bounds

Retrodict【追溯】

Predict Other

Inform Data Collection

Estimate【估计，预测;报价，预算书;评价，判断】 Hidden Parameters

Calibrate【校准;使标准化;使合标准;测量（枪的）口径】

 

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　　　　Using Models to Decide，Strategize，and Design

[Real Time]Decision Aids

 

{In the Monty Hall problem just described, should you stick with your original door or should you switch

After Monty eliminates one door, your chance of choosing the door with the prize remains one in three. The sum of probabilities has to add up to one. So the chance of the prize being behind one of the two doors you didn't initially select has to be two in three. Of those two doors, one is open and reveals nothing, so the other has a two in three chance of concealing the prize.}

 

Comparative Statics

Counterfactuals【反设事实】

Identify and Rank Levers

Experimental Design

Institutional Design【制度性；体制；机构的】

Help Choose Among Policies and Institutions

 

 

 

Peer Effect

{同群效应顾名思义，“同群效应”就是中国古语所谓“近朱者赤，近墨者黑”。它所指的是这样一种现象：一个人的行为不仅受到价格、收入等个体自身经济利益的激励影响，同时也会受到他周围的与他相同地位的其他人影响。}

{同群效应（peer effect），在一些经济学著作里，也被叫做“social capital”、“contagion”、“neighborhood effeets”或者“peer group effects”。}

Granovettor's[诺维特] Model

Aggregation{n. [地质][数] 聚合，聚集；聚集体，集合体}

Model

 *N Individuals[n. [经] 个人；[生物] 个体（individual的复数）]

 *Each has a Threshold[n. 入口；门槛；开始；极限；临界值]

   -Tj for person j

   -Join if Tj others join

{注释：如果没有person的threshold阀值为zero，那么这件事永远不会发生，

the tail's able to wag[摇摆；摇动；饶舌] the dog}

Collective Action

More Likely If:

    -Lower Thresholds

    -More Variation in thresholds

The Standing Ovation[热烈欢迎；大喝采] Model

Analyze：

Threshold to Stand: T

Quality: Q

Signal: S=Q+E

Initial Rule

   -If S>T, Stand

Subsequent[adj. 后来的，随后的] Rule

    -Stand if more X% stand

 

 

 fertility　　【n. 多产；肥沃；[农经] 生产力；丰饶】

 

 

 

The Identification Problem

Homophily[n. 同质性]

dynamic[

• adj. 动态的；动力的；动力学的；有活力的
• n. 动态；动力
  • adj. 动态的；动力的；动力学的；有活力的
  • n. 动态；动力]

 

 

Aggregation[n. [地质][数] 聚合，聚集；聚集体，集合体]

More is Different

Actions

Single Rule

Family of Rules

Preferences

Central Limit Theorem[n. [数] 定理；原理]