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Economics brief: six big ideas.
經濟概要：六大經濟思想。
Information asymmetry: Secrets and agents
信息不對稱：秘密和代理
George Akerlof's 1970 paper, “The Market for Lemons”, is a foundation stone of information economics, the first in our series on seminal economic ideas.
六大經濟思想之一，喬治·阿克洛夫1970年的論文——《檸檬市場》，它是信息經濟學的一塊基石。
In 2007 the state of Washington introduced a new rule aimed at making the labour market fairer: firms were banned from checking job applicants' credit scores.
2007年，華盛頓州引入了一項旨在讓勞動力市場更公平的新法律：企業被禁止核查求職者的信用得分。
Campaigners celebrated the new law as a step towards equality—an applicant with a low credit score is much more likely to be poor, black or young.
發起這項運動的人歡呼慶祝，認為這是通向平等的一步——信用得分低的求職者極有可能是窮人、黑人或者年輕人。
Since then, ten other states have followed suit.
自那以后，又有十個州如法炮制。
But when Robert Clifford and Daniel Shoag, two economists, recently studied the bans, they found that the laws left blacks and the young with fewer jobs, not more.
但是，日前，當兩位經濟學家——羅伯特·克利福德和丹尼爾·紹格——研究了這些禁令時，他們發現，這些法律帶給黑人和年輕人的工作更少了，而不是更多。
Before 1970, economists would not have found much in their discipline to help them mull this puzzle.
放在1970年之前，經濟學家是不會在這門學科中找到太多的東西來幫助他們仔細思考這個迷的。
Indeed, they did not think very hard about the role of information at all.
實際上，他們當時根本就沒有很努力地去思考信息的作用。
In the labour market, for example, the textbooks mostly assumed that employers know the productivity of their workers—or potential workers—and, thanks to competition, pay them for exactly the value of what they produce.
例如，那時的教科書大都假設，在勞動力市場中，雇主知道他們的工人——或者潛在的工人——的生產率，而且，由于競爭，是按照工人所生產的東西的價值給他們開工資的。
You might think that research upending that conclusion would immediately be celebrated as an important breakthrough.
人們可能認為，顛覆這一論斷的研究立即會被譽為一項重大突破。
Yet when, in the late 1960s, George Akerlof wrote “The Market for Lemons”, which did just that, and later won its author a Nobel prize, the paper was rejected by three leading journals.
然而，當喬治·阿克洛夫于上世紀60年代末期寫出恰恰實現了這種突破并為作者贏得了諾貝爾獎的《檸檬市場》時，這篇論文曾遭到三家主要期刊拒絕。
At the time, Mr Akerlof was an assistant professor at the University of California, Berkeley; he had only completed his PhD, at MIT, in 1966.
那時，阿克洛夫是加州大學伯克利分校的一名助教；僅于1966年在麻省理工完成了博士學位。
Perhaps as a result, the American Economic Review thought his paper's insights trivial.
也許是因為這個原因，《美國經濟評論》認為他的論文的觀點微不足道。
The Review of Economic Studies agreed.
《經濟研究評論》同意了這個看法。
The Journal of Political Economy had almost the opposite concern: it could not stomach the paper's implications.
《 政治經濟學雜志》有著幾乎完全相反的擔憂：它可能消化不了這篇論文深遠意義。
Mr Akerlof, now an emeritus professor at Berkeley and married to Janet Yellen, the chairman of the Federal Reserve, recalls the editor's complaint: “If this is correct, economics would be different.”
如今已是伯克利分校名譽教授并同美聯儲主席珍妮特·耶倫成婚的阿克洛夫還記著那位編輯的不滿：“如果這是正確的，經濟學會截然不同。”
In a way, the editors were all right.
從某種程度上來說，這些編輯當時都是對的。
Mr Akerlof's idea, eventually published in the Quarterly Journal of Economics in 1970, was at once simple and revolutionary.
最終于1970年在《經濟學季刊》上發表了的阿克洛夫的思想即是簡單的，也是革命性的。
Suppose buyers in the used-car market value good cars— “peaches” —at $1,000, and sellers at slightly less.
假設，二手車市場中的買方給好車—— “桃子” ——估價1000美元，賣方要稍微少一點。
A malfunctioning used car—a “lemon” —is worth only $500 to buyers (and, again, slightly less to sellers) .
一輛瑕疵二手車—— “檸檬”，對買方而言，只值500美元 (而且對賣方來說，又要稍微少一點)。
If buyers can tell lemons and peaches apart, trade in both will flourish.
如果買方能夠區分檸檬和桃子，兩者的交易都會紅火起來。
In reality, buyers might struggle to tell the difference: scratches can be touched up, engine problems left undisclosed, even odometers tampered with.
在現實中，買方可能會設法找出不同：刮痕可能被補上了，發動機問題可能未得到披露，甚至里程表都可能被篡改了。
To account for the risk that a car is a lemon, buyers cut their offers.
為了對車是檸檬的風險負責，買方大肆殺價。
They might be willing to pay, say, $750 for a car they perceive as having an even chance of being a lemon or a peach.
比如說，他們可能愿意為一輛他們認為有著或是檸檬或是桃子的同等幾率的車支付750美元。
But dealers who know for sure they have a peach will reject such an offer.
但是，確切地知道自己的車是桃子的交易者將拒絕這樣的出價。
As a result, the buyers face “adverse selection” : the only sellers who will be prepared to accept $750 will be those who know they are offloading a lemon.
結果，買方面臨 “逆向選擇” : 唯一準備接受750美元的賣家將是知道自己正在脫手檸檬的人。
Smart buyers can foresee this problem.
聰明的買方能預見到這個問題。
Knowing they will only ever be sold a lemon, they offer only $500.
由于知道自己永遠只會被賣給檸檬，他們僅出價500美元。
Sellers of lemons end up with the same price as they would have done were there no ambiguity.
最后，檸檬的賣方得到的是與沒有歧義時會得到的價格同樣的價格。
But peaches stay in the garage.
但是，桃子還在倉庫中。
This is a tragedy: there are buyers who would happily pay the asking-price for a peach, if only they could be sure of the car's quality.
這是一種悲劇：只要能確信汽車的質量，會高高興興地為桃子支付詢價的買方是存在的。
This “information asymmetry” between buyers and sellers kills the market.
買賣雙方之間的這種 “信息不對稱” 殺死了市場。
Is it really true that you can win a Nobel prize just for observing that some people in markets know more than others?
僅僅因為觀察到市場中的某些人比別人知道得多就能獲得諾貝爾獎這種事是千真萬確的嗎？
That was the question one journalist asked of Michael Spence, who, along with Mr Akerlof and Joseph Stiglitz, was a joint recipient of the 2001 Nobel award for their work on information asymmetry.
這曾是一名記者向邁克爾·斯彭斯——這位與阿克洛夫和約瑟夫·斯蒂格利茨一起因為他們對信息不對稱的研究而獲得2001年諾貝爾獎的聯合得主——問到的問題。
His incredulity was understandable.
他的懷疑是可以理解的。
The lemons paper was not even an accurate description of the used-car market: clearly not every used car sold is a dud.
檸檬論文甚至不是一篇關于二手車市場的精準描述：很明顯，不是每一輛在售二手車都是有瑕疵的車。
And insurers had long recognised that their customers might be the best judges of what risks they faced, and that those keenest to buy insurance were probably the riskiest bets.
另外，保險商早就承認，他們的客戶可能是其自身所面臨的風險的最佳判定者，最急于要投保的可能是風險最大的賭博。
Yet the idea was new to mainstream economists, who quickly realised that it made many of their models redundant.
然而，這個思想對于主流經濟學家來說全新的，他們很快就認識到它已讓他們的許多模型顯得多余。
Further breakthroughs soon followed, as researchers examined how the asymmetry problem could be solved.
沒過多久，隨著研究者檢驗不對稱問題能得到怎樣的解決，進一步的突破隨之而來。
Mr Spence's flagship contribution was a 1973 paper called “Job Market Signalling” that looked at the labour market.
斯彭斯的主要貢獻是1973年的一篇名為 “就業市場信號行為” 的考察勞動力市場的論文。
Employers may struggle to tell which job candidates are best.
雇主可能難以挑出最好的那個求職者。
Mr Spence showed that top workers might signal their talents to firms by collecting gongs, like college degrees.
斯彭斯指出，頂層的工人或許會以收集榮譽——如大學學位——的行為為信號，向企業展示自己的才華。
Crucially, this only works if the signal is credible: if low-productivity workers found it easy to get a degree, then they could masquerade as clever types.
關鍵是，這只有在信號是可信的時候才管用：如果低生產力的工人發現得到學位很容易，他們就可能把自己裝扮成聰明之人。
This idea turns conventional wisdom on its head.
這一思想徹底顛覆了傳統的智慧。
Education is usually thought to benefit society by making workers more productive.
一般認為，教育之有益于社會，是因為它讓工人變得更高效。
If it is merely a signal of talent, the returns to investment in education flow to the students, who earn a higher wage at the expense of the less able, and perhaps to universities, but not to society at large.
如果它僅僅是才華的一個象征，教育投資的所得就會流向學生，使他們以才華較少之人為代價獲得更高的工資；或者也可能是各個大學，但不是整個社會。
One disciple of the idea, Bryan Caplan of George Mason University, is currently penning a book entitled “The Case Against Education”.
這個思想的一位信徒——喬治梅森大學的布萊恩·卡普蘭目前正在撰寫一本名為《反對教育之種種》的書。
(Mr Spence himself regrets that others took his theory as a literal description of the world. )
(斯彭斯本人后悔的是，被人把他的理論當成是對這個世界的一種文字描述。)
Signalling helps explain what happened when Washington and those other states stopped firms from obtaining job-applicants' credit scores.
信號行為有助于解釋華盛頓等州在阻止企業獲得求職者信用得分時所發生了的事情。
Credit history is a credible signal: it is hard to fake, and, presumably, those with good credit scores are more likely to make good employees than those who default on their debts.
信用歷史是一個可信的信號：它難以造假，而且，可以假定，信用得分良好的人比債務違約的人更有可能成為好雇員。
Messrs Clifford and Shoag found that when firms could no longer access credit scores, they put more weight on other signals, like education and experience.
克利福德先生和紹格先生發現，當企業不再能得到信用得分時，會把重點放在其他信號上面，如教育和資歷。
Because these are rarer among disadvantaged groups, it became harder, not easier, for them to convince employers of their worth.
因為這些信號在弱勢劣群體中較為少見，因而，對他們而言，讓雇主相信自己的價值就變得更難，而不是更容易。
