我今年再也不寫了

我停筆了!!

The Future of Economics

Something that I 'partially' agree with. From MR:

In my possibly overdogmatic view, economics is most useful when its models are relatively simple and intuitive. We've run out of new models which are simple and intuitive. So the theory game is over. The standard, old data sets have been data mined to death. We're now on to the "can you build/create your own data set?" game. That game can and will last for a long time; in some ways it will favor go-getter extroverts just as the theory game favored introverts.

I think theory still has a bright future. The fact that our current models are flawed means that we can still find better ones. Whether or not they are still simple and intuitive is another thing, but that depends on the modeler's skill. Good theorists can still provide us with simple and plausible economic models.

Sometimes for new discoveries to occur, we need to throw away the old framework that we have been working with for so long. When marginal analysis was introduced to economics, it catapulted our subject to the forefront of social sciences. When information asymmetry was introduced, every subject in economics was fundamentally changed. We are at the edge of another breakthrough, I think.

Am I too optimistic?

A Good Question

Another Application of Game Theory

From Freakonomics blog. Game theory and test taking, from Dixit and Nalebuff's new book: The Art of Strategy.

Consider the following question for the GMAT (the test given to MBA applicants). Unfortunately, issues of copyright clearance have prevented us from reproducing the question, but that shouldn’t stop us.

Which of the following is the correct answer?
a) 4π sq. inches
b) 8π sq. inches
c) 16 sq. inches
d) 16π sq. inches
e) 32π sq. inches

O.K., we recognize that you’re at a bit of a disadvantage not having the question. Still, we think that by putting on your game-theory hat you can still figure it out.

Before reading their analysis, take a shot at trying to reason your way to the correct
answer.

Here’s what they said:
The odd answer in the series is c. Since it is so different from the other answers, it is probably not right. The fact that the units are in square inches suggests an answer that has a perfect square in it, such as 4π or 16π.

This is a fine start and demonstrates good test-taking skills, but we haven’t really started to use game theory. Think of the game being played by the person writing the question. What is that person’s objective?

He or she wants people who understand the problem to get the answer right and those who don’t to get it wrong. Thus wrong answers have to be chosen carefully so as to be appealing to folks who don’t quite know the answer. For example, in response to the question: “How many feet are in a mile?” an answer of “Giraffe,” or even 16π, is unlikely to attract any takers.

Turning this around, imagine that 16 square inches really is the right answer. What kind of question might have 16 square inches as the answer but would lead someone to think 32π is right? Not many. People don’t often go around adding π to answers
for the fun of it. “Did you see my new car — it gets 10π miles to the gallon.” We think not. Hence we can truly rule out 16 as being the correct solution.

Let’s now turn to the two perfect squares, 4π and 16π. Assume for a moment that 16π square inches is the correct solution. The problem might have been: “What is the area of a circle with a radius of 4?” The correct formula for the area of a circle is πr^2. However, the person who didn’t quite remember the formula might have mixed it up with the formula for the circumference of a circle, 2πr. (Yes, we know that the circumference is in inches, not square inches, but the person making this mistake would be unlikely to recognize this issue.)

Note that if r = 4, then 2πr is 8π, and that would lead the person to the wrong answer of b. The person could also mix and match and use the formula 2πr^2, and hence believe that 32π or e was the right answer. The person could leave off the π and come up with 16 or c, or the person could forget to square the radius and simply use πr as the area, leading to 4π or a. In summary, if 16π is the correct answer, then we can tell a plausible story about how each of the other answers might be chosen. They are all good wrong answers for the test maker.

What if 4π is the correct solution (so that r = 2)? Think now about the most common mistake: mixing up circumference with area. If the student used the wrong formula, 2πr, he or she would still get 4π, albeit with incorrect units. There is nothing worse, from a test maker’s perspective, than allowing the person to get the right answer for the wrong reason. Hence 4π would be a terrible right answer, as it would allow too many people who didn’t know what they were doing to get full credit.

At this point, we are done. We are confident that the right answer is 16π. And we are right. By thinking about the objective of the person writing the test, we can suss out the right answer, often without even seeing the question.

Now, we don’t recommend that you go about taking the GMAT and other tests without bothering to even look at the questions. We appreciate that if you are smart enough to go through this logic, you most likely know the formula for the area of a circle. But you never know. There will be cases where you don’t know the meaning of one of the answers or the material for the question wasn’t covered in your course. In those cases, thinking about the testing game may lead you to the right answer.

The joke is on us

From ptt:

1. 看不見的手
一群功夫學生要畢業了, 老師諄告他們: 出去以後, 千萬不能和經濟學家過招,因為他們都有一隻看不見的手.

2. 市場萬能
學生: 既然市場是萬能的, 那麼我們還要經濟學家有什麼用?
老師: 因為經濟學家能給我們帶來快樂, 而這是市場做不到的.

3. 完全競爭
第一天, 上帝創造了太陽, 接著魔鬼創造了灼傷;
第二天, 上帝創造了性, 隨後魔鬼創造了婚姻;
第三天, 上帝創造了一位經濟學家, 而魔鬼陷入了沉思...思前想後了好一陣子, 魔鬼也創造了一位經濟學家.

4. 預測衰退
經濟學家預測出了過去5次衰退中的9次.

5. 經濟學家定律
經濟學家第一定律: 對任何一位經濟學家而言, 一定存在著一位實力旗鼓相當的同時觀點又針鋒相對的經濟學家.
經濟學家第二定律: 他們都是錯的.

6. 論文發表
問: 你應該到哪裡發表論文?
答: 如果你能理解並能證明, 那麼就寄給數學雜誌;
如果你能理解但無法證明, 那麼就寄給物理學雜誌;
如果你不能理解但能證明, 那麼就寄給經濟學雜誌;
如果你既不能理解也無法證明, 那麼就寄給心理學雜誌.

7. 總統的困惑
美國總統和俄羅斯總理在高峰會談的間歇閒聊. 俄羅斯總統對美國總統說: 你知道嗎, 我遇到了一個麻煩. 我有一百個衛兵,但其中一個是叛徒而我卻無法確認是誰.
美國總統則說: 這算不了什麼. 令我苦惱的是我有一百個經濟學家,而他們當中只有一人講的是事實, 可每一次都不是同一個人.

8. 智慧的顯現
一位經濟學家去華盛頓的自然歷史博物館參觀. 當站在恐龍化石面前時, 他對身邊的遊客說: 這只恐龍的歲數足足有20億年又10個月.遊客驚訝且恭敬地問道: 您從哪裡得到如此準確的信息? 經濟學家不無自豪地回答說: 10個月前我來此參觀過. 那時講解員告訴我這只恐龍已經20億歲了.

9. 經濟與政府行為
如果經濟在運轉, 那就徵稅;
如果經濟不斷地在運轉, 那就監督;
如果經濟停止運轉, 那就補貼.

10. 學派之分
問: 要多少個經濟學家才能把一個壞燈泡換掉? 答: 八個. 一個把燈泡裝上, 剩下的負責保持其他條件不變.
問: 要多少個芝加哥學派的經濟學家才能把一個壞燈泡換掉? 答: 一個也不用. 要是燈泡壞了, 市場機制自然會把它更換.
問: 要多少個新興古典學派的經濟學家才能把一個壞燈泡換掉? 答: 那就要看當時的工資如何.
問: 要多少個凱恩斯學派的經濟學家才能把一個壞燈泡換掉?
答: 愈多愈好. 因為這樣便可增加就業, 刺激消費, 使得總合需求曲線向右移.

11. 經濟與天氣
問: 上帝為何創造經濟學家?
答: 因為有經濟學家的話, 天氣預報便顯得準確得多了!

12. 理論與實證
假如有一千名經濟學家去處理換燈泡的問題, 當中會有十個理論經濟學家, 各人對換燈泡的方法有不同的主張.餘下的990個實證經濟學家就努力地去檢驗那一個的理論正確. 最後, 所有人仍是在黑暗之中.

13. 諾貝爾經濟學獎
唯有經濟學這一門學科, 會出現兩位學者互唱反調, 而他們卻分享著同一個諾貝爾獎.

14. 誠實與說謊
甲: 聽說經濟學家總在說謊. 你能否告訴我, 如何判定他在說謊?
乙: 經濟學家大都比較誠實, 很少掩飾. 你只要注意他的嘴就行了, 嘴一動就在說謊了.

15. 經濟學家的語言
美國聯邦儲備委員會主席格林斯潘的名言: 如果你覺得聽懂了我說的話, 那你一定是誤解了我的意思.

16. 絕對真理
一位經濟學家宣稱: 慶賀生日是一項有益身心健康的活動.統計數據表明, 一個人一生中歡度的生日越多, 他的壽命就越長.

17. 做愛什麼是經濟學家? 知道100做愛方法, 卻從未與異性交往的人.

18. 病毒
如果社會是電腦, 經濟學家就是病毒. 可大致分類如下:
利益集團經濟學家病毒: 其作用是把硬碟分割許多小單位, 每個單位均無任何實際用途,卻都聲稱自己是本機器上最重要的部件.
計量經濟學家病毒: 染上此病毒後, 60%的機器將在14%的時間裡丟失38% (正負3個百分點) 的數據.
政治經濟學家病毒: 佔用記憶體但不幹活, 只有到下次選舉才能清除.
政府經濟學家病毒: 你的系統無法工作, 但所有診斷程序都報告說一切正常.
社會主義經濟學家病毒: 造成當機, 毀掉硬碟, 並堅決否認此事發生過.
主流經濟學家病毒: 聲稱受到電腦上其他文件威脅, 並以「自衛」為借口刪除他們.
中央銀行經濟學家病毒: 確保它自己大於其他所有文件.
跨國公司經濟學家病毒: 刪除所有貨幣文件, 微笑著發出經濟即將變好的信息.
供給學派經濟學家病毒: 讓你的電腦沉睡4年, 醒過來卻發現債務增加了三千個億.
環境經濟學家病毒: 阻止你刪除任何文件.

19. 明天/昨天/今天
經濟學家到明天才會知道為什麼昨天預言的事情在今天沒有發生.

20. 錯誤
經濟學家就是這樣一種人, 他並不知道他所談論的. 但是, 他讓你覺得這是你的錯誤.

21. 社會主義/共產主義/資本主義
在社會主義制度下, 如果你有兩隻母牛, 你送一隻給鄰居, 以體現友好.
在共產主義制度下, 如果你有兩隻母牛, 你把它們送給國家, 而國家供應你牛奶.
在資本主義制度下, 如果你有兩隻母牛, 你賣掉一隻母牛, 以所得收入再購進一隻公牛.

I personally like 3, 5, 7, 14, and 20

Who is better? Jordan vs. Kobe

This confirms what I have thought all along:

As you can see, out of necessity Jordan was taking on a large offensive responsibility early in his career; as his teammates got better, he slowly eased back on the workload, and his efficiency improved as a result. Kobe's story is the opposite: with great teammates early, he didn't have to do as much, but when Shaq left before the '05 season, Kobe was actually forced to take a larger role in the offense than even Jordan ever had to.

It's more interesting, though, to look at the efficiency levels the players maintained vs. their % of possessions used. The mark of a truly great offensive player is to maintain a high level of efficiency while taking on a large share of the team's offensive responsibility, and even though Kobe's numbers are impressive, Jordan is consistently more efficient than Bryant no matter if he's using more possessions or not. Also, note the translated defensive ratings: aside from their age-21 seasons, MJ is better (sometimes vastly so) at every turn.

In other words -- and this should be obvious -- when we watch Kobe play, we're seeing a far lesser version of Michael Jordan in action. Similar in style and mannerism, maybe, but when we translate the statistics for era, it becomes very clear that Jordan was actually the one "playing chess" while Bryant "plays checkers."

我笑了

星期一發考卷，我發現我的成績都是2倍的成長。