經濟學中途島

經濟理論可以證實或證偽嗎？

laniaho — Thu, 27 Jan 2011 07:18:13 +0000

在所有社會科學甚至自然科學的方法論討論中，實證主義（positivism）都早已遭遇猛烈攻擊，但經濟學似乎是個例外，不僅方法論的討論不太多，且大多數經濟學家依然習慣抱著實證主義（或者修改一下成為證偽主義）不放。

姑且先撇開對於實證主義本身的方法論批評；仔細想想，經濟理論真的都能以符合實證主義的方法加以證實或證偽嗎？

According to Varoufakis Yanis（1998）Foundations of economics: a beginner’s companion, section 11.3 『Why economics theories cannot be judged by the facts』：

Consider the basic hypothesis of the neoclassical approach: ‘All rational people are maximisers.‘ ……there are indeed many tests we can conduct in laboratories to find out if people behave in a manner consistent with the principles of utility maximisation. The problem is that such tests are not likely to settle the debate in favour or against the neoclassical hypothesis the people are maximisers.

If people turn out to maximise utility, neoclassical economists can modify their hypothesis subtly, for example they may put forward the amended hypothesis: ‘There is something that people maximise.‘ Perhaps there is. The problem is that this hypothesis can never be refuted, nor can it be verified. If we establish that people do not maximise utility, the defender of neoclassical economics can always turn around and say: ‘But how do you know that there is not something that they maximise?‘ The answer is: we cannot know. Thus the hypothesis that people maximise cannot be proved wrong(i.e. refuted) in which case we have a theory motivating all economic testbooks which is beyond the empricists’ and positivists’ method of theory appraisal.

‧註一：上面這段文字所批評的現象看來是真實存在的，比如賽局理論中關於「人是否自私」的那一大串實驗經濟學研究，或者如Gary Becker與《蘋果橘子經濟學》那樣，把「誘因」的定義放得無限寬廣。

‧註二：有一些經濟學家認為，60歲以前不要碰方法論問題，那是創造力枯竭的傢伙幹的事情，而且容易走火入魔。這話不無道理。但在做研究的過程中，方法論問題總還是會在這裡那裡冒出來，所以有空思考一下似乎也不錯。
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到目前為止，我曾在一些場合聽到經濟學家對此問題的兩種回答。

第一種可以算是方法論的標準答案，就是：經濟學與其他科學一樣，有許多自明的「公理」，例如上面提到的「效用最大化」。這些「公理」類似於基本定義，本就不是可以證實或證偽的對象；證實與證偽，是針對依據這些公理所推衍出來的種種命題與宣稱才能夠進行。這有點類似拉卡托斯的「核心-保護帶」說。

第二種回答比較妙。該經濟學家老實承認確有此問題，不過無所謂，只要能夠自圓其說、自得其樂就行了。呵呵。

產能利用率與失業

laniaho — Fri, 21 Jan 2011 13:40:37 +0000

美國經濟學家Mark Thoma發了篇文章，指出美國的製造業產能利用率的走勢過去都與失業率走勢相符，但1990年代中期以後卻日漸脫節，如此圖所示（注意，代表產能利用率的紅線是100-C.U.，即紅線往下走才表示產能利用率提升，往上走反而是下降）：

從圖中可以看出，大約在1996年左右，這兩條數列開始出現較大差異，在2000年dot.com泡沫破裂之前，失業率持續下降，但產能利用率也呈現下降，泡沫破裂之後，失業攀升，產能利用率則更進一步下降。2002-2003年左右，產能利用率開始回升，失業率也下降，但兩者之間始終有一段不小的差距。等到2007年次貸危機爆發，兩者皆快速下降，但當產能利用率在2010年左右觸底反彈之後，失業率依然沒有太大起色。

另一個有趣的時間點是在1992年前後。那時的產能利用率已經從1989年的那次危機中回升，但失業率卻繼續下降一段時間，之後才出現回升。

兩者的同向變動並不令人意外，最奇怪的是：1.出現了產能利用率下降，但失業率不升甚至下降；其次，稍微比前者可以理解一點的是：2.產能利用率上升，但失業率不下降或者延遲下降。第一種現象看起來似乎只出現在1997-2001年期間，但使得此後十年兩率數值差距拉大；第二種現象則出現多次，從圖上看來包括1974、1977、1992、2003、2010等年份。

Thoma在文章中提了四點理由：1.企業不確定景氣前景，因此雇用策略保守；2.企業利用危機進行生產重組，降低了雇用需求；3.公司本就沒有解雇熟練的老工人；4.產業出現較大重組，工人需學習新技能才能找到新工作。這四點都是文獻上常談到的，基本上都是在解釋第二種現象，也就是失業率作為落後指標的特性，嚴重一點就是所謂的「無就業復甦（Jobless Recovery）」。

不過，第一個現象又是為什麼呢？

這裡就先不講下去了，有興趣的不妨自己找資料、動動腦囉。

Music Break: Ποίηση-Φαίδων θεοφίλου-Η Λειτουργία της Μήθυμνας, by Angelique Ionatos

laniaho — Sun, 19 Dec 2010 01:09:21 +0000

讀經濟學論文，看多了希臘字母，也來聽點希臘音樂吧！

Michael Hudson：New $600B Fed Stimulus(QE2) Fuels Fears of US Currency War

laniaho — Wed, 10 Nov 2010 08:52:06 +0000

（不知為何，我無法嵌入Democracy Now網站上的影片，只好從youtube轉。Democracy Now網頁有該段訪談的逐字稿如下）

JUAN GONZALEZ: President Obama is leaving today for a ten-day visit to Asia, with scheduled stops in India, Indonesia, South Korea and Japan. In South Korea, Obama will attend the G20 meeting, where US monetary policy is expected to be high on the agenda.

On Wednesday, the Federal Reserve said it will pump $600 billion more into the US economy and keep interest rates at historically low levels. The short-term impact of the Fed’s move, known as quantitative easing, has been a jump in stock prices across the globe, but many nations have accused the US of waging a currency war by devaluing the dollar. Brazil’s president-elect Dilma Rousseff said, quote, 『The last time there was a series of competitive devaluations, it ended in World War II.』

China has accused the US of uncontrolled money printing. By devaluing the dollar, the Fed is cheapening the price of US exports and making foreign imports more expensive. In addition, the low interest rates are encouraging US corporations to make massive investments overseas, cheaply buying up foreign real estate, natural resources and stock.

AMY GOODMAN: Our next guest, Michael Hudson, says finance has become a new form of warfare. Michael Hudson is Distinguished Research Professor at University of Missouri, Kansas City. A former Wall Street economist, he is the author of many books, including Super Imperialism: The Economic Strategy of American Empire.

Michael Hudson, welcome to Democracy Now!

MICHAEL HUDSON: Thank you.

AMY GOODMAN: Why warfare?

MICHAEL HUDSON: Well, the object of warfare is to take over a country’s land, raw materials and assets, and grab them. And in the past, that used to be done militarily by invading them. But today you can do it financially simply by creating credit, which is what the Federal Reserve has done. It’s created $600 billion. It hasn’t gone into the economy. The head of the Fed is known as 『Helicopter Ben』 because he talks about dropping money into the economy. But if you see helicopters, they’re probably not your friends. Don’t go out and wait for them to drop the money, because the money is all going electronically into the banks. And the Fed has said, we want to give the banks so much money that they will lend it out so you can begin to bid up prices on real estate again and pull the banks out of the real estate negative equity that it’s in. So the purpose, according to the Fed, is to raise the price of real estate, to inflate asset prices. But that’s not happening. The actual banks have lent less today than they did in 2007. So the money is going abroad. And it’s going abroad not really to buy foreign companies so much, but to speculate in currency.

Now, the Fed and the Congress, two weeks ago, said, 『We want China to raise its currency by 20 percent.』 This would create billions and billions of dollars of bonanza for Wall Street banks, and it would enable them to earn their way out of debt by essentially looting the China central bank, the Brazilian central bank, the Turkish central bank and the other central banks, because you can now borrow money in America at one percent. So you’d put down, let’s say, a billion dollars of your own—a million dollars of your own money, borrow $99 million of the bank’s money—that’s $100 million. You would buy Chinese currency, RMB, for $100 million. You then say, 『Raise your currency by 20 percent,』 which is what the Fed has asked them to do. That means that your million dollars now has turned into a $20 million gain, because $100 million is now worth $120 million. You’ve made a 200 percent profit. And for Wall Street, they deal in billions, not millions. And so, this would enable the banks to make up their money by buying out, essentially, foreign currency. They’re doing the same in Australia. It’s currency gamble.

JUAN GONZALEZ: Well, and meanwhile, the impact, because obviously this decision was made the day after the elections at the Fed meeting, they saw what the political landscape was. There wasn’t going to be any kind of stimulus coming from Congress, so they had to come up with a stimulus for Wall Street the day after the elections. But the impact on the American people of maintaining these historically low interest rates—you know, as we were talking earlier before the show, if you have a little bit of money in a savings account right now, you’re getting virtually no interest. So you’re, in essence, being pressured to end up going into the stock market to be able to get any kind of return on your money—those who still have savings. The same thing with the pension funds. What’s happening to the American people as a result of this same kind of policy?

MICHAEL HUDSON: Well, if they have money to put in pension funds or savings, they’re only able to get about one percent, if they keep it safe. Otherwise, they’re taking a risk in the stock market. But the key is not simply lowering interest rates. The idea is to flood the economy with credit so the banks will lend out more debt. And if the Fed’s policy works, then housing prices are going to go back up so high that most consumers are going to have to pay 40 percent of their income for housing. They’re going to have to pay more money for credit card debt. The purpose is to help the banks make money at the expense of the economy. It’s not to help the economy at all. That’s the really important thing. When they say the economy, they mean—the Fed means its constituency: the banks. And the banks’ product is debt. And that’s what they’re trying to produce.

AMY GOODMAN: Is this inflationary?

MICHAEL HUDSON: It will inflate asset prices. It won’t inflate consumer prices. It’s actually deflationary for consumer prices, because if you’re an American consumer and you spend 40 percent of your income for housing, 15 percent for debt service to the bank, 11 percent goes out in your FICA wage withholding, and about ten to 15 percent in actual income taxes, that means that the average American has maybe one-third or a quarter of their salary to actually spend on goods and services. So they have to spend so much on debt service and finance and insurance and real estate that there’s no money to buy goods and services, so that’s why so many stores are closing throughout the cities on the big shopping streets. It’s deflationary for the economy, inflationary for the people who have wealth, inflationary for the banks. And it’s the banks really at the expense of the economy.

JUAN GONZALEZ: But there is the reality now that the world has changed dramatically over the last thirty or forty years, and you have now this sort of new independent force on the world scene, even in finance, which is the countries like China, Brazil and other countries of the third world that are, in essence, standing up on some of these issues. What’s happening in terms of their reaction?

MICHAEL HUDSON: The world is dividing into two currency blocs. And over the last few months, China has gone to Turkey, Malaysia, Thailand, and said, 『We want to avoid using the dollar altogether.』 They’re treating it like a pariah currency. They’re saying, 『Well, let’s make a currency swap. We’ll give you our Chinese RMB, you give us your currency, the baht, and we’ll do our trade in our own currency. We are isolating the dollar, so that people are not going to use the dollar anymore.』 That’s why the dollar is plunging on world foreign exchange markets. The whole world that America created after World War II of open markets is now closing off. And it’s closing off, really, because the United States is trying to rescue the real estate market from all the junk mortgages, all the crooked loans, all of the financial fraud, instead of just letting the fraud go and throwing the guys in jail like other economists have suggested.

AMY GOODMAN: I want to play a comment from the Nobel Prize-winning economist Joseph Stiglitz. We interviewed him recently. He was talking about the Federal Reserve and its attempt to inject liquidity into the US economy.

JOSEPH STIGLITZ: So the money isn’t going into the American economy. The lending is actually below what it was in 2007. In a globalized economy, the money is looking for the best place to go. And where is it finding it? In the emerging markets. So, the irony is that money that was intended to rekindle the American economy is causing havoc all over the world. Those elsewhere in the world say, what the United States is trying to do is the twenty-first century version of 『beggar thy neighbor』 policies that were part of the Great Depression: you strengthen yourself by hurting the others. You can’t do protectionism in the old version of raising tariffs, but what you can do is lower your exchange rate, and that’s what low interest rates are trying to do, weaken the dollar. The flood of liquidity abroad is trying to push the exchange rates abroad. And they say—they’re saying, 『We can’t allow that.』

AMY GOODMAN: That’s economist Joe Stiglitz. Professor Hudson, your response?

MICHAEL HUDSON: That was, I think, the best interview on your show that Professor Stiglitz has ever done. Last Saturday, I was in Germany at an economic meeting, and we were discussing this very interview there. And what they’re pointing out is that in Europe, in Germany and all of Europe, it’s illegal for the central bank to finance government debt. All of Europe is being subjected to austerity now because of the way in which their constitution is written. So they’re saying, 『Wait a minute. When we run a deficit, we have to raise interest rates and impose austerity. And in the United States, they are doing just the opposite. They’re lowering interest rates to buy us out.』

And the interview of Professor Stiglitz here was quite right. America is doing all of this. The Fed is doing this to cover up the huge fraud that he talks about. He’s right. These people should be in jail, and you shouldn’t bail them out. You’re keeping the debt that was run out by the junk mortgages and the fraudulent lending, you’re keeping that in place, pricing American labor out of the market, and making it impossible for America to earn its way out of debt. So, in Europe, they’re saying, 『How can America ever repay these dollar debts that they’re running up?』 They can’t repay, and that’s why the euro is going up against America. And that’s why they say, 『We want to now talk to the BRIC countries, to China, to the third world, and move into a currency area with them and just isolate the dollar, so they can’t do the kind of financial warfare that they’ve been engaging in.

JUAN GONZALEZ: Well, in terms of how countries can respond, one of the things that obviously a lot of the Asian countries did during the financial crisis in late 1990s was currency controls—in essence, trying to prevent foreign capital from either leaving or entering the country. Is that something that you envision something this country is beginning to do?

MICHAEL HUDSON: Yes, there is only one country that did that, and that was Malaysia under Prime Minister Tun Mohamad Mahathir. He would not sell the domestic currency to the foreign speculators, so George Soros and the others who sold the currency short, hoping that the central bank would use all of its money just to defend its currency and then be emptied out, they couldn’t cover their position, so they were squeezed. But countries like Korea, where the meetings, the G20 meetings, are this week—the IMF went and said, 『You owe money you can’t pay. George Soros has raided you. You have to sell Americans your electric companies. You have to sell Americans your car companies.』 And this was a grab that, in the past, in past centuries, there would have had to be a military invasion to take over. And now they’re doing it financially. And they’re angry over there.

AMY GOODMAN: You were advising Kucinich when he was running for president.

MICHAEL HUDSON: Yes.

AMY GOODMAN: What is—overall, what do you think President Obama should do, and what do you think he did wrong, since people say it’s the economy that took him down in the elections?

MICHAEL HUDSON: He has always represented Wall Street’s interest. The deal he—his protector in the Senate was Joe Lieberman and part of the Democratic Leadership Council. And during the last presidential campaign, he won because he said he was for change. And Dennis Kucinich kept saying, 『Here is the change in the law that I’ve recommended.』 He said exactly what he would do. Mr. Obama never said what he would do. And it’s obviously the case that he saw that the public wanted change. If you want to get elected, you say that you’re for change.

But what he’s turned into is the third Bush-Cheney administration. He’s reappointed the worst of the Bush people, like Tim Geithner as the Treasury secretary. He’s kept on the most right-wing of the Clinton people as his economic advisers. He is essentially in Wall Street’s pocket. And that’s not changed at all. And that’s why so many people were so disappointed. They believed that he was going to be for change, and he’s a good speaker, but he had no intention of doing the change at all, as we now see.

And he still has not come out and said that America needs anything except more debt, more bailouts for the banks. People were angry because the banks were bailed out. And now the Republicans will say he didn’t give them enough. They’re angry because he didn’t give Wall Street enough and cut taxes enough on the rich. That’s not why people are angry. They’re angry because he gave money to the rich, the exact opposite. So, I guess you could say Mr. Obama and Mr. Kucinich are at opposite ends of the political spectrum.

AMY GOODMAN: What should he do right now?

MICHAEL HUDSON: What he should do is, essentially, bring the debts down to the ability to pay. He had promised that he was going to renegotiate mortgages to the current value of housing. That would mean writing down housing by about 30 percent, so it could be affordable again. But he hasn’t done that. In the government, he has prevented the state attorney generals from prosecuting financial fraud and from forcing the banks to renegotiate the mortgages down to what American consumers can afford. And Mr. Obama has blocked this. And so, all fifty—

JUAN GONZALEZ: And also what the real value of many of those properties are.

MICHAEL HUDSON: The market—either the market price or the rental price. So, essentially, people would pay for the—to own a house pretty much what you’d pay to rent. That’s the definition of equilibrium in economics. But right now they’re paying much more on their mortgage than they could go and rent an apartment for, and they can’t afford it. People are out of work. And the result is that there is a debt squeeze. And so, that’s why I said this is deflationary, not inflationary. What should be inflated are American wages, American living standards, tangible investment. Instead, what’s inflated is debt and the financial sector at the expense of the production and consumption.

JUAN GONZALEZ: And what do you expect to happen at the G20 meeting that’s coming up now?

MICHAEL HUDSON: The same thing that happened two weeks ago: absolutely nothing. They will all agree that the soup was very good, that the food was nice, and that they will have further discussions. But America will not get any of what it’s asking for from them, because they’re going to say, 『Look, we’re not going to let you create electronic keyboard credit and buy out our real estate and our industry and empty out our bank reserves like you did in the 1997 Asia crisis.』 That’s never going to happen again, and the world is going to begin splitting into two currency blocs: the BRIC bloc and the dollar bloc.

AMY GOODMAN: We’re going to have to leave it there, Michael Hudson, president of the Institute for the Study of Long-Term Economic Trends, distinguished research professor of economics at University of Missouri, Kansas City, author of Super Imperialism: The Economic Strategy of American Empire.

China, global imbalances and poor countries – Reading Notes 2010.11.09

laniaho — Tue, 09 Nov 2010 16:53:20 +0000

‧The Renminbi and Poor-Country Growth – OECD （摘要版：Global imbalances, the renminbi, and poor-country growth – VOX）

關於中國經濟，目前很多人批評它拼命出口到歐美國家（低估人民幣）累積外匯，造成全球經濟失衡。這篇OECD的paper換個角度，從其他發展中國家的角度，談中國的發展對其他較窮的發展中國家有何影響，以這角度切入目前關於中國經濟的辯論。

大致可分成兩部分。第一部份是研究中國經濟成長對於其他國家的影響，迴歸分析發現對於其他窮國大致是正面的。研究中還指出，2000年以後中國的競爭優勢確實出現提升；1997年之前中國產品對其他低收入的發展中國家具有價格壓力，而在1997年之後則是對中等收入的發展中國家造成壓力，對低收入國家則否。

第二部分則是將此種影響帶入目前的人民幣匯率爭論，指出人民幣快速升值對於其他發展中國家也有害，因為其他國近年來得益於中國經濟的帶動，如果人民幣快速升值（超出其應該有的、根據自身發展情況的逐步升值）而使中國經濟減速，這些發展中國家（尤其是窮國）將連帶受到衝擊。

但應注意，前面提過，中國產品目前對中等收入國家具有價格壓力，所以如果人民幣升值，中等收入國家可以在價格競爭方面得到利益；不過，由於這些國家目前同時也得益於中國成長的帶動效果，所以人民幣升值帶來的效應將是一正一負，總的結果並不確定。

同時，由於中國的生產效率高於其他發展中國家，因此即使中國的生產有一大部份因為人民幣升值而轉移到其他國家，就發展中國家整體而言，也不會帶來與中國生產同等的成長（例如減貧）效果。

‧Global Imbalances: An unconventional view – IDEAs

這篇更特別，俄羅斯的這位Vladimir Popov對各發展中國家壓低匯率進行出口導向發展的模式給予正面肯定，認為這似乎是目前看來唯一可行的趕超戰略，而西方國家除了美國與英國之外，貿易逆差都不算高，應該還可以承受更多債務，如此將能改變數百年來落後國家與先進的西方國家差距不斷擴大的趨勢。

這觀點非常片面，不過確實說出了一些有趣的東西，而且是大白話。

There is strong evidence that the accumulation of reserves can spur long-term growth in developing countries, although not in rich countries. If all countries use these policies, all will lose, and, on top of that, for developed countries this policy does not work. But for developing countries it works, and there are good reasons why these countries should have sufficient policy space to use this tool to promote catch up development.

Accumulation of reserves means that the country saves more than it invests, produces more than it consumes, providing its savings to finance investment and consumption in other countries. This may sound like a drag on development; it is often argued that capital should flow from rich to poor countries because K/L ratios are lower in developing countries and hence the returns on capital are greater. However, this is only one effect. The other effect is a dynamic one and it works in a completely opposite direction: if a country manages somehow to become competitive in the world markets (either through higher productivity or through lower wages or through low exchange rate), it starts to export more than it imports and develops a trade surplus. If this surplus is stored in the form of foreign exchange reserves, the exchange rate gets undervalued and the trade surplus persists. That is why countries that develop faster than the others usually have a trade surplus (United States in the twentieth century before the 1970s, Japan and Germany after the Second World War, East Asian Tigers and Dragons and China, of course). Accumulation of reserves (that are invested in reliable short-term government securities and yield very low interest rates) implies losses to the national economy (Rodrik, 2006), but every policy has costs – this is a price to pay for promoting growth.

The argument against the policy of reserve accumulation and undervaluation of the exchange rate for developing countries is the following: if all poor countries would pursue this policy, developed countries would finally accumulate unsustainable levels of debts and the inevitable subsequent adjustment could be painful.

But even today the debt of the rich countries is not that high. US has net international indebtedness of about 30% of GDP, Euro area has net international liabilities of 16% of GDP, and Japan is a net creditor with net international assets of nearly 50% of GDP.

As the table below suggests, it is exactly developing countries that are the major international debtors, whereas developed countries (with a notable exception of US and UK) are mostly net creditors; so there is still room for the West to go into debt.

To conclude, reserve accumulation works as a development tool (theoretically, every externality could be taken care of through taxes, but in practice selective policies rarely work). Because protectionism is currently de facto outlawed by WTO, exchange rate protectionism is the only available tool for promoting catch up development, in a way – the instrument of last resort. Reserve accumulation in poor countries will not continue forever; it will come to an end, once they catch up with the West. Meanwhile, developed countries get a chance to consume more than they produce. Why not go into debt to help the global South catch up with the West sooner?

Regulation for innovation；Immigration – Reading Notes 2010.11.04

laniaho — Thu, 04 Nov 2010 03:33:56 +0000

這兩篇關於勞動市場的研究乍看之下有些反常識，但其實都挺合理：

‧Labor Laws and Innovation – NBER

Stringent labor laws can provide firms a commitment device to not punish short-run failures and thereby spur their employees to pursue value-enhancing innovative activities. Using patents and citations as proxies for innovation, we identify this effect by exploiting the time-series variation generated by staggered country-level changes in dismissal laws. We find that within a country, innovation and economic growth are fostered by stringent laws governing dismissal of employees, especially in the more innovation-intensive sectors. Firm-level tests within the United States that exploit a discontinuity generated by the passage of the federal Worker Adjustment and Retraining Notification Act confirm the cross-country evidence.

1980年代與自由化、私有化一同興起的「彈性化（flexibilization）」論，差不多把「解除勞動市場管制」無限上綱，不論是工作福利、勞動條件、團體協約、工作內容等等各種層面的規約，皆排上了應予彈性化的清單。但其實在當時就有不少修正主義路線的研究指出：某一面向的彈性化可能需要其他面向的』rigidity』作為補充或支撐，比如有好的福利保障才能激發工人更靈活彈性的工作表現，因此完全的彈性化在現實上未必可行或有效。這篇NBER的研究就屬於這種。

‧Immigration and productive tasks: Can immigrant workers benefit native workers? – VOX

Several studies find that immigrants do not harm the wages and job prospects of native workers. This column seeks to explain these somewhat counterintuitive findings by emphasizing the scope for complementarities between foreign-born and native workers. Examining 14 European countries from 1996 to 2007, it finds that immigrants often supply manual skills, leaving native workers to take up jobs that require more complex skills – even boosting demand for them. Immigrants replace “tasks”, not workers.

一般人談到移工（or外勞），講的都是他們搶了我們的工作的「替代效果」，但其實移工也會有「互補效果」，也就是低階勞工增加，與其配合的高階勞工也會相應增加，一減一加，總的結果「未必」會使本國工人失業增加。只要是比較嚴謹的文獻都會提到這一點，可惜一般都只拿「外勞搶工作」的部分出來講，於是便形成了強烈的刻板印象。

當然，這裡仍有一個難題：被移工替代的與因移工而補上的，在現實上通常並非同一群人，形成低階的「受害」而高階的「受益」，兩類工作之間的流動絕非想像中容易。

Music Break：Godowsky‧Renaissance, Gigue in E major, by Magdalena Baczewska

laniaho — Fri, 15 Oct 2010 01:58:23 +0000

被彷彿無窮無盡的工作與課業追趕著～～我絕不認輸！

Inventory Cycle 存貨週期

laniaho — Sat, 02 Oct 2010 16:05:36 +0000

寫報告時注意到這個東西：Inventory Cycle，譯成「存貨週期」。What’s this?

先來段名詞解釋：

Inventory Cycle: Also termed stock cycle, an inventory cycle is the fluctuation of GDP caused by the accumulation and the selling of stocks/inventories. If production is greater than demand, GDP will rise but companies will also accumulate unsold stocks. This will encourage some to scale back production, cutting GDP even if demand remains constant. An economic cycle is created and normally the inventory cycle amplifies the existing economic cycle as stocks are accumulated in good times and production is reduced in bad times.

In the global recession of 2008, demand plunged, leaving companies with significant unsold inventory. They responded by mothballing factories leading to a plunge in industrial production, output and GDP. Once the stock was sold output rose again purely because some production lines were restarted.

Source: Chris Giles, Economics Editor, Financial Times

然後，以下這篇2008年的文章把基本涵意解釋得很清楚：

存貨增加是景氣衰退警訊 by 于國欽【2008/09/21 工商時報】

　　1929年秋，美國股市的崩盤，一直被認為是造成此後4年美國經濟大蕭條的元凶，但愈來愈多的證據顯示，這個事件的因果關係應該反過來看，也就是早在股市崩盤前夕，美國所得分配惡化，導致中產家庭購買力下滑，進而無法消費，使得汽車、家電、服飾存貨激增，終致生產停滯，信心滑落，才是引起這一波經濟恐慌的真正原因。

　　從國民所得統計來看，生產面所編算的GDP應等於從支出面估得的 GDP，但事實上，當年度的生產是否全數在當年度支用掉？當然不會，而當生產出來的貨品沒有等額的需求加以吸收時，其結果就會出現大量存貨，1929年前夕的美國，表面榮景下即已出現此一隱憂。

　　現今天各國所編算的國民所得統計，基本上仍以生產面做為基準。

　　但是觀察今天各國所編製的國民所得統計，多數國家生產面(供給面)所編算出來生產毛額始終與支出面(需求面)所編算出來的一致，例如台灣2007年從生產面算得的GDP為12.6兆元，從支出面估得的 GDP也是12.6兆，難道這麼巧，當年所生產的財貨全數被當年支用了嗎？當然不是，那麼沒有被支用的財貨跑到哪裡了呢？答案是跑到存貨這個項目了，雖然存貨並非經濟學家凱因斯所說的「有效需求」，但廣義而言，存貨也被計入國內投資毛額中，以今年國內投資毛額2 .8兆中，即含有新增的存貨130億元。

　　因此，今天各國所編算的國民所得統計，基本上還是以生產面做為基準，所公布的經濟成長率(GDP的實質增幅)呈現的也是生產面的景況，至於所生產的財貨有多少成為凱因斯所講的有效需求？那就必須回到需求面，重新檢視存貨的變化，如果GDP成長伴隨著存貨激增，那便是一個警訊。

　　存貨可以概分為原材料、在產品、產成品及批發零售，通常在國際原物料價格預期將大漲時，為求降低成本，廠商必定會增加原材料存貨，例如1973年、1974年原油穀物價格不斷上揚，因此原材料的「存貨增加」由30億元倍增至132億元、306億元，隨著通膨率升逾40％， 1974年囤積存貨風氣大盛，產成品的「存貨增加」也由前一年的12億元驟增至262億元。

　　回顧美國景氣在1984年底急轉直下，台灣存貨在1984年、1985年也呈升高，但這和10年前的石油危機不一樣，並非油價大漲，而是美國景氣衰退，因此台灣的存貨以「產成品」為主，存貨增加由1983年的 2億元連兩年激增至百億元以上，這一次存貨這項指標也提前反映了景氣下挫的走勢。

　　最近一次的經濟衰退發生在2001年，依經濟部工業生產調查，製造業存貨率在2000年底衰退前夕竟快速由第3季的65％升至77％，於次年2月升至83％，提前預告50年來最迅猛的衰退即將到來，當時沒有人相信衰退會降臨台灣，但衰退終究發生了，逾50萬人失業、商業蕭條、逾5千家工廠關門，這一年經濟成長率為-2.2％。

　　從存貨所反映的經濟走向，明年遽升的數額無疑是嚴重警訊。

　　顯而易見的，由於同一年度的生產未必全數成為有效需求，因此從生產面估得的GDP，其快速增加未必代表經濟大好，惟有參考「存貨增加」的變化，才能正確地理解景氣的走向。而若想更即時瞭解存貨率的變化，那就得逐月查看一下工業生產的調查結果，如此相互核實，才能更準確地研判經濟前景。

　　在全球受到美國次貸風暴的衝擊下，美國經濟重創，尤其日前隨著美國第四大投資銀行雷曼兄弟聲請破產後，更令人看不清這一波景氣何時見底，而台灣出口雖暫時仍有不錯的成績，但「存貨增加」卻已悄悄走高，估計今年第四季將激增104億元，明年更將升至259億元，從歷史上存貨所反映的經濟走向，這無疑是嚴重的警訊。

　　依國民所得統計原理而言，生產面與支出面所編製的GDP應呈雙面平衡，但實務上由於統計誤差在所難免，不可能如此神準。其實，部分國家如今已不強求雙面平衡了，如中國國家統計局所編製的生產面 GDP於2006年達21.18兆元人民幣，但同年度由支出面編算出來的GDP 卻是22.12兆元，其間相差近5％，這樣的編法雖可能使人疑惑到底該以哪個版本為準，但卻可免於為了調整雙面平衡，而影響存貨統計的精確性，從而可以更精確地掌握有效需求的實況。

◎台灣的存貨統計資料：

1. 主計處→（總體）統計資料庫→國民所得統計→資本形成毛額→存貨增加。
立法院好像有將此資料整理在：中央政府總預決算查詢及統計資料庫→總體經濟資料庫→台灣地區工業生產統計資料→製造業存貨率/製造業存貨量指數

2. 經濟部統計處→工業產銷存動態調查→存貨率。不過要查詢詳細數據好像需要付費成為會員。另一個方法是從資料庫如AREMOS去找。

壕溝戰是囚犯困境嗎？Is Trench Warfare a Prisoner’s Dilemma？

laniaho — Tue, 07 Sep 2010 12:40:35 +0000

我當兵受訓的時候，跟大家一起摸魚，上課要挖傘兵坑之類自然也只是做做樣子，教官有時也無可奈何。有一次跟同梯一群人在下課時半開玩笑地問教官：你看我們現在的樣子，會不會擔心到時候沒辦法打仗啊？

只見教官笑著說，1996年台海危機時，他當時人在金門，發現平常混水摸魚的士兵，這時不用特別盯，一個一個都變得非常積極，自動去擦槍堆沙包。他說：要是真的開戰，你自己上戰場，敵人就在你面前，不是你死就是他死的時候，現在不開槍不挖洞的，到時自動就會了。

正如那個教官所說，一般印象中，戰場上的敵對雙方，大概是最不可能出現合作行為的人群。不過，歷史上卻真有案例違背這種一般印象，而且是在雙方廝殺極為慘烈的戰爭中，兩軍對峙拉鋸之際，敵對陣營的士兵違背自己軍官的指令，自發地停火，對方不開槍我也不開槍，沒有任何協議，卻維持某種奇妙的「合作」關係。

這是怎麼一回事呢？

最近在《A Quantitative Tour of the Social Sciences》這本書裡讀到一個有趣的段落，談賽局理論中囚犯困境概念的應用分析，背景是第一次世界大戰（基本上是歐戰）西線戰場上的壕溝戰，焦點便是上述的、出現於敵對雙方士兵之間的奇妙合作現象。

（圖中紅線即為壕溝戰沿線，所謂西線）

■ 壕溝戰是什麼？

先介紹一下背景。霍布斯邦（Eric J. Hobsbawm）在《極端的年代》一書中如此描述此壕溝戰的歷史場景：

德軍在宣戰之後五、六周，經過中立的比利時等地，挺進直入法國，卻在巴黎東邊幾十里外的馬恩河（Marne）上被擋住了（後來在1940年時，德方的計畫則成功了）。然後德軍撤退了一些，雙方臨時造起防禦工事——法方有比利時所餘地區相助，以及英國一支地面部隊支援。英方這支軍力，後來變得極為龐大。這兩道防線相互平行，延伸極快，從佛蘭德斯地區（Flanders）沿英吉利海峽一帶，一直抵達瑞士邊境，連一絲縫隙也沒有。法國東部和比利時一大部分地方，因此便落入德軍手裡。以後的三年半裡，雙方對峙的情況不曾有過任何重大的改變。

這就是所謂的「西線」（Western Front），西線戰事從此成為人類戰爭史上前所未見的殺戮戰場。幾百萬人隔著沙袋築起壁壘，彼此虎視。他們日夜在戰壕裡面，過著像老鼠跳蚤般的日子，事實上根本也就是人鼠同居。將領們一再想要突破對峙的僵局，於是每回攻擊令一下，便是幾晝夜，甚至幾周長無休止的炮火轟擊——日後一位德國作家將之形容為「一陣陣鋼鐵狂風」——企圖「弱化」敵人，迫其轉入地下。然後時機一到，我軍便爬越沙包，身上密密纏繞一圈又一圈帶有倒刺的鐵絲圈作為保護，一浪一浪擁入此時已成「無人的地界」：舉目一片狼藉，積水成潭的彈坑，連根倒的樹幹，泥漿滿身的棄屍。大夥兒繼續前進，一直到敵人的機關槍——其實每個人心裡都有數——再將他們掃射倒地為止。

德軍在1916年（2月到7月）曾試圖突破凡爾登（Verdun）的防線。那一仗總共有200萬兵員交手，死傷即達100萬人。可是德方沒有得逞。為了迫使德軍停止在凡爾登的攻勢，英方在索姆河（Somme）發動攻擊。這一仗打下來，英軍犧牲了42萬人——其中有6萬人，在頭一天攻擊行動裡就告喪命。這次大戰西線的戰爭，以英法兩國部隊為主，難怪在兩國人民的腦海中，這次大戰才是真正的「大戰」，遠比二戰慘烈多了。法國在這場大戰裡面，失去了兩成兵役年齡的男子。我們若再將俘虜、傷兵、終生殘廢、容貌被毀者——這些「面目全非」之人，戰後成為活生生的戰爭寫照——一道算進去，法國每3名軍人裡面，恐怕只有一人能夠毫髮無損地打完這場大戰。英方也好不到哪裡去，500餘萬兵員當中，能夠全身而退者不知有多少。英國整整失去了一代——50萬名30歲以下的男子在大戰中身亡——其中尤以上層階級損失最重。這一階級的青壯年人生來就得做紳士、當軍官，為眾人立榜樣，在戰場上身先士卒，自然也就先倒在敵人的炮火之下。1914年從軍的牛津、劍橋學生，25歲以下者半數不幸為國捐軀。德國損失人數雖然遠超過法國，但由於它軍事年齡總人口高出更多，死亡比例就比較小了——13％。比起來，美國的損失顯然少得多（美軍陣亡人數11．6萬名，英國近80萬，法國160萬，德國180萬），但同樣可以證明西線戰事的殘酷，因為這是美軍唯一參與的戰區。兩相比較，美國在二戰陣亡的總人數，雖是上一次大戰的2.5近3倍之多，可是1917－1918年間美方的軍事行動，就時間上而言，幾乎不到一年半，而二戰卻長達三年半；就地點上來說，也只限於狹小一區，不似二戰全球作戰規模的龐大。

■ 士兵的生活

如此慘烈的戰事，怎麼還能夠容許敵對士兵之間的自發「合作」出現呢？確實，西線戰場上，敵對雙方通常是處於你死我活的情境。但如果聚焦於個別士兵的生活，情況可能就完全不同。

在雅克‧梅耶（Jacques Meyer）《第一次世界大戰時期士兵的日常生活（1914~1918）》一書中，作者記錄了當時的法國士兵對德國士兵的看法。他指出，在你來我往殊死戰鬥之中，仇恨確實是常見的情緒，即使是最熱愛和平的人也經常被瘋狂殺人的衝動所控制。不過，作者也指出：

對於敵人的仇恨並不是他們慣常的精神狀態…內地的仇敵情緒遠比前線強烈，說到前線的仇敵情緒，司令部比部隊強烈，部隊比炮隊強烈，炮隊比指揮所強烈，指揮所又比戰壕或者哨卡強烈，到了戰壕或者哨卡，仇恨已經降到最低限度了。

士兵們往往覺得「那些可憐的傢伙和我們一樣」：

1916年，在一個步兵小班裡，我們發現，士兵們並不想隨隨便便就襲擊對面那些被他們稱作「另一些人」的戰士們，他們和我們一樣可憐。真正打仗的人根本沒有後方萊茵河兩岸的人所固有的民族仇恨，我們所看到的（德國）士兵有的死了有的被俘，和我們自己的遭遇極其相似。

更有趣的是下面這一段記載：

我們對面是德軍警備軍的一個步兵團…雙方的主要交流活動就是互相喊話，交換香菸、報紙。但是誰走出戰壕做這些事呢？鬼子率先邀請法國士兵：』過來吧，我們不會說出去的！』『不，你過來，我這裡有菸。』這種交流很少有結果，因為德軍或者我軍方面的軍官會走過來禁止大家說話……（有一天）正午時分，一名德國兵和一名法國兵分別站著走出了戰壕，雙方幾百名士兵都目不轉睛。此時此刻不止一個人將手指摳在步槍的扳機上，一旦形勢不對隨時準備開槍。他們走到了一起，談了談戰爭，談了談戰士們受的苦，然後點了兩根煙，沒有發生別的事情。

■ 賽局理論之囚犯困境

怎麼理解這種現象呢？

Robert Axelrod在其名著《The Evolution of Cooperation》（1984）中，以賽局理論中的囚犯困境分析這種現象。Axelrod認為，短期而言，敵對雙方士兵的最大利益是開槍射擊，不論對方是否還擊，因為只要開槍（不與敵方合作）就有殲滅敵人的機會而使自己的處境更好。換句話說，礙於種種困難而無法互相溝通協調的敵對士兵，便是限於囚犯困境之中。

以賽局理論而言，在一次或有限期的賽局裡，每個人的最佳策略應該都是不合作，因為彼此都理性地預見到最後一局對方會不合作，於是反推回來每個人每一局都不會合作。

那麼，在壕溝戰的例子中，這種合作是如何達成的？Axelrod的解釋是：壕溝戰的特色之一是僵持不下的戰局，而這將單次賽局的囚犯困境轉變為重複賽局，從而改變了參賽者的策略選擇。

在單次賽局裡，不合作者不需擔心引起對方的報復，因為賽局一次就結束了。但在無限期的重複賽局裡，一方的背叛將引起對方的報復，接著引起我方的再報復，永無寧日。在這種情況下，一方便可能採取有條件的策略，展現克制以換取另一方的合作，以某種方式達成互惠。

Axelrod認為，這其中採取策略其實很簡單，只要雙方都採取同樣的TFT（Tit For Tat）策略（所謂「以牙還牙以眼還眼」）就行了。此一策略是指對手作什麼你也作什麼，比如對手開槍你也開槍，對手停火你也停火，如此便能在對立嚴重、也沒有辦法直接溝通的情況下，達成互惠合作的結果。Axelrod認為，在重複賽局中，透過反覆的試探與模仿，雙方士兵將「演化」出TFT作為最佳策略。

但是，在《A Quantitative Tour of the Social Sciences》這本書裡，編者兼作者之一的Andrew Gelman則認為，Axelrod可能搞錯了問題的方向，因為壕溝戰其實根本不是什麼囚犯困境。

前述Axelrod的出發點是認為士兵短期的最佳策略是開槍射擊，也就是不合作策略，而現實歷史卻違背這一點，於是才提出理論加以解釋。但Andrew Gelman則認為，在兩軍對陣的壕溝戰中，士兵一開槍就暴露了自己的位置，將引來對方的射擊，置自己於生命危險之中，因此，合理的反應應該是不開槍。如此一來，個別士兵並沒有首先開槍的動機，「合作」會帶來短期利益，因此其實是很自然的選擇，沒有什麼賽局囚犯困境的問題，根本不需要任何特別的解釋。

Andrew Gelman還認為，如果真有什麼賽局，那也是存在於士兵與其指揮者之間，因為士兵不想開槍而指揮者則採取種種方式強迫士兵開槍。Axelrod的錯誤，則可能是來自於常識性地以為對陣的兩軍就是利益衝突的敵人，卻沒有注意到對於前線的個別士兵而言，對敵方的一個士兵開槍於己並無任何好處。

從賽局理論的角度，Gelman認為，與其用囚犯困境模型來分析，不如以coordination games分析較具解釋力。

■ 政策與政治意涵

最後談一點政策與政治問題。

在政策意涵上，一如Gelman指出，Axelrod的理論建議，政策導向是要塑造一個重複賽局的情境，從而使參賽者具有為了長期利益而合作的動機。而Gelman的理論則建議，要為參賽者提供短期的利益誘因，同時注意排除外部破壞者（如壕溝戰例子中的雙方指揮者）的影響。

更有趣的是政治意涵上的差異。

Gelman文中指出，Axelrod的理論試圖在一個互相競爭、幾乎沒有合作可能的環境中，找出促成合作的條件與策略，樂觀地相信人們可以為了長期的利益而超越短期的利益，政治上接近自由主義。不過，由於Axelrod認為士兵的短期利益是開槍，而不是如許多自由主義者那樣，著重指出其實是指揮者不受節制的權力造成了互相衝突的困境；這又近於保守主義。

至於Gelman自己的理論，似乎比自由主義更激進。他關於「若有賽局也是存在於士兵與其指揮者之間」的看法，可以說是畫出了一條階級界線，表達了類似「一將功成萬骨枯」的意思。也就是說，敵對陣營的士兵與士兵之間其實是具有相同利益的，反倒是他們與其上的指揮官（軍官）之間，並沒有必然的合作關係。

我不知道Gelman本人的政治立場，那也與這裡談的沒有直接關係。這裡的重點是，Gelman上述理論的政治意涵，其實接近於第一次世界大戰時，革命派的社會主義者（例如列寧、羅莎盧森堡）所主張的：各國工人農民（構成各國士兵的主體）具有共同利益，應該互相團結，將槍口轉向自己本國的統治階級，將對外戰爭變為本國的革命起義。

Gauss, Leopardi and Statistics

laniaho — Thu, 12 Aug 2010 15:24:52 +0000

德國數學家高斯（Carl Friedrich Gauß）（上圖），與義大利詩人李奧帕迪（Giacomo Leopardi）（下圖），兩人有什麼共同點？

1. 生活時代相近。（不過高斯從1777活到了1855年，李奧帕迪則短命得多，1798到1837，不到40歲就掛了）

2. 都是男人！（這點當然是說來湊數的…）

3. 好吧，我要說的真正重點是：他們都跟統計學有關。

學過一點統計學的人，或多或少都被那個高斯馬可夫定理（Gauss-Markov Theorem）折磨過，從此無法忘記高斯的大名。而我最近除了被這個定理折磨之外，還在一本小說裡見到了高斯。

在《丈量世界》這本傳記式小說裡，高斯談到他正在進行的研究是：

…一種死亡統計，高斯說完先喝了口茶，但隨即臉色大變，厭惡地將茶杯往外推，推到不能再遠為止。大家總認為，我們的存在方式是由自己決定的。人生是由我們自己開創、發掘的，我們努力賺錢，找到心愛的人，愛這個人甚於愛自己，然後生小孩，小孩或許聰明，或許愚蠢。然後看著自己心愛的人去世，自己也逐漸衰老、變笨，最後病了，終於也入土為安。大家總以為，這一切都是我們自己決定的。但數學告訴我們，我們只是選擇了一些較為寬廣的路走。

我不知道高斯實際上有沒有表達過類似的看法，但從統計學出發做此聯想，還算合情合理。

至於李奧帕迪跟統計學，那純粹是個意外。

第一次知道李奧帕迪，是因為John Berger的《The Sense of Sight》，但除了書中那篇動人的文章之外，我一直沒有直接讀過李奧帕迪的作品。直到最近偶然想起，才去圖書館和網路上搜尋他作品的英譯本（比如這裡）。

詩人跟統計學固然沾不上邊，我卻意外在其作品《Thoughts》中，讀到這樣一段話：

In every land the universal vices and ills of mankind and of human society are noted as peculiar to that place. I have never been anywhere where I have not heard, ‘Here the women are vain and inconstant, they read little, and they’re poorly educated. Here the public are curious about other people’s affairs, and they’re very talktive and slanderous. Here money, favour, and baseness can achieve anything. Here envys rules, and friendships are hardly sincere,’ and so on and so on, as if things went on differently elsewhere. Man are wretched by necessity, and determined to believe themselves wretched by accident.

這段帶有統計學色彩的哲理話語，跟小說裡高斯所說的話，還挺異曲同工的。