Category Archives: economics

Optimists and Pessimists

Today it seemed that I had nothing better to do so I picked up two guys and went to a seminar. It was about "Optimists and Pessimists", or more specifically, the title was Insurance and Perceptions: How to Screen Optimists and Pessimists, offered by Johannes Spinnewijn from London School of Economics as a series of UPF Microeconomics Seminar. Well, I should admit that he is really young (just graduated from MIT last year)...Although there is no decent published papers listed on his CV, according to today's speech, he is supposed to be a good researcher and teacher.

As the titled says, his paper is about how to distinguish two kinds of people in the insurance market: who are optimistic and who are pessimistic. He has got some interesting conclusions by separating the optimistic behaviors into two kinds: baseline-optimistic and control-optimistic. Then follows the discussions in competitive market and monopoly market respectively, there appears the different actions what the agent and principal take. I love one of his conclusion that "people with heterogeneous abilities or risks, but identical perceptions cannot be separated" while "people with different perceptions can be separated with a menu of screening contracts, even when the true abilities or risks are the same". That indicates (I hope I understand it correctly) the expectation plays a more important role than the true abilities when deciding people's behavior. Thus, whatever your true ability is, your attitude partly decides the situation you are facing/living in. At the end, he also considered the government's role and regulation/subsides, but that was not what I really cared about then.

At last, one interesting episode. Mas-colell suddenly appeared when the seminar was going. I was shocked because I've heared that Mas-colell didn't really take part in teaching or any thing else related to our program or GSE. But he appeared... It seemed that he was still caring about what the latest economic researches are doing. Great! (But anyway, during the discussion, he didn't say any words...)

(the temporary loss of my Chinese blog forces me to post in English... Is it good or bad? I have no idea... )

The social network of economists

Recently I fell in love with social network... Therefore, it is unavoidable to add some social network analysis results into my graduation thesis. Here are some interesting graphs used in my paper, which I would like to share with you online. They are all about "the social network of economists", i.e. the academic circle of economics.

all_10_nolabel

Full view of the economists' world, without labels.

The bigger size of nodes denotes the higher level of connections with others (degree/pagerank). (2000-present). An expandable vector diagram can be download here:  all_10_nolabel.pdf
top_10_grey

Full view of economists' world, with grey edges (2000-present)

all_10_main_all_label

The structure (reduced) of economists' social network, with labels of names (2000-present).

An expandable vector diagram can be download here: all_10_main_all_label.pdf

[Update July]

Here is a specific analysis of the "Law and Economics" sub-field. Data source is from all published papers (6,319 in total) under JEL classification K: Law and Economics. Available at RePEc.org.

law and economics

Here is the PDF version: academic circle of law and economics.pdf

You can find more graphs by continuing reading.
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[Play Econometrics with R] Preview for Chapter 1-2 released!

I'm glad to announce that now the preview version for my brochure Play Economics with R has been released! This time I publish the first two chapters, which were just finished several days ago. At present it is written in Chinese, so there is only an English content for none-Chinese readers.

Content

Chapter 1 Get familiar with R

1.1 Data Import...................................... 6
1.2 Summary the data....................................... 7
1.2.1 Average value..................................... 7
1.2.2 Linear regression (ordinary least squares, OLS).................... 8
1.3 Plot a regreesion figure...................................... 9
1.4 Point prediction......................................... 10
1.5 Multiple linear regression..................................... 10
1.6 Save and edit the code.................................... 11
1.7 Search for help....................................... 11

Chapter 2 Start from cross-section data

2.1 Parameter test....................................... 12
2.1.1 t test..................................... 13
2.1.2 F test..................................... 13
2.2 Confidence Intervals....................................... 14
2.3 Dummy variables....................................... 14
2.3.1 grouped by the nature.................................. 14
2.3.2 grouped by the value................................. 14
2.3.3 interaction items................................... 15
2.3.4 specify the based group.................................. 17
2.4 Heteroscedasticity test...................................... 18
2.4.1 BP test (Breusch-Pagan Test)........................ 19
2.4.2 White test (White test for heteroskedasticity)................ 20
2.5 Robust standard deviation...................................... 20
2.6 Weighted least squares estimation (WLS).............................. 21
2.6.1 with disturbance form known ............................... 21
2.6.2 feasible generalized least squares (Feasible GLS, FGLS)................ 22
2.7 Generalized Linear Estimation (GLM)................................. 24
2.7.1 Maximum Likelihood Estimation (MLE).......... 25
2.7.2 Probit and Logit models.............................. 25
2.7.3 Tobit model................................... 26
2.7.4 Ordered Logit / Probit............. 27
2.8 Count Model............................... 28
2.8.1 Poisson Regression Model................... 28
2.8.2 test for dispersion.............................. 29
2.8.3 Negative binomial regression model............. 30
2.8.4 Zero-inflated Poisson model (ZIP)............ 30
2.9 Sample Selection Bias.................................... 32
2.9.1 Heckit model.................................. 32
2.10 Simultaneous Equations Model..................................... 33
2.10.1 two-stage least squares (2SLS) and instrument variable................... 33
2.10.2 Simultaneous Equations Model Estimation: Seemingly Unrelated Regression (SUR)... 34
2.11 Proxy Variables....... 35

Download

You may download it from GitHub: http://github.com/cloudly/Play-Econometrics-with-R/downloads (I'll keep updating this page)

Please tolerate the mistakes and typo, as well as some formatting problems I need to come over in the future.

News and Feedback

If you want to keep up with the latest news of this brochure, please send an email to: publication@cos.name or cloudlychen@gmail.com

Your feedback is welcome! Please also send to publication@cos.name or cloudlychen@gmail.com

What‘s Next?

I'm currently working on Chapter 4 Panel Data Analysis (so I skip Chapter 3 Time Series temporarily). Chapter 4 will include several interesting methods, like Fixed / Random Effect, Panel Data tests and GMM estimator, etc. Please tell me what you are looking for in my brochure and I'll add them if possible.

What Do We Pay For Asymmetric Information? The Mechanism Evolution of Reputation, Punishment and Barriers to Entry in Online Markets

Well, in fact it is not a piece of news. It is the title of a paper I wrote last winter. After finishing it, I went on doing something else and forgot it. Now it is already a new spring, I do not want to submit it to any journals since I have nothing fresh to add into it. Without anything new, I don't have the incentive to edit it. Therefore, I share it with you here.

Title

What Do We Pay For Asymmetric Information? The Mechanism Evolution of Reputation, Punishment and Barriers to Entry in Online Markets

Abstract

The appearance of the Internet reduces transaction costs greatly, and brings the boom of online markets. While we are trying to regard it as the most realistic approximation of perfect competition market, the asymmetric information and a series of problems caused by it stop us from dreaming. As the old saying goes, there is no free lunch. This summer witnessed the collapse of the reputation system in Taobao, the biggest online transaction website in China. In fact, during the evolution of mechanisms in online markets, reputation, punishment and barriers to entry have been established in turn. What do we pay for maintaining these mechanisms? In which circumstance will they be effective?

In this paper I try to build a series of models within the principal-agent framework and repeated games to explain why and what we should pay for asymmetric information while enjoying shopping online. Specifically, these mechanisms are considered step by step and their boundary validation conditions are discussed. Finally, as the conclusion indicates, in a larger range that a mechanism is effective, the more opportunity cost should be paid as a rent for information.

Download (English Version)

Copyright Announcement: Please do not change any content without my permission. Please do not use it for commercial purpose. Please do not publish it anywhere else.

If you would like to mention or quote it in your article, please link it to this page or copy this link: What Do We Pay For Asymmetric Information? The Mechanism Evolution of Reputation, Punishment and Barriers to Entry in Online Markets

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