今年的諾貝爾獎頒給了「貧窮經濟學」的辛苦研究人員。一邊作翻譯這篇文章一邊作討論。筆者看完後覺得小有趣的一個「存在主義的現實」，又有一番人性悲哀和無奈 - 何以「窮人社會」能以何種經濟方式存在，而機制和效率是如何產生的？倒也可以給這其他世上稍富裕及發達的國家的經濟學者和企業主們啟示。

「貧窮經濟學」是30年前開始，在總體經濟學上不少人熱衷的大謎團。針對從鄉村農業社會至都會工業社會的各層面或多或少有些研究文章出來過，但是沒有明顯的「變數」來說明貧窮的直接、間接原因及關係公式的提出。

諾貝爾經濟學獎委員會就這樣頒給目前最具創意、最有學養人文關懷的學者們，就是在哈佛大學任教的Havard Kremer，從生物學和化學隨機法得到的啟示，於是選定前提，不是亂選的，而是找出和總體經濟發展最相關的因子來作操縱變因，健康、教育、技能的指標來著手，看這些方面的變化過程而能從中獲益。他跑去肯亞作「田野調查」，在肯亞，他隨機地把學校的學生作分配，並分為兩大類，一類為有作「政策性地協助介入」，一組則沒有這麼作，就是placebo對照組，他作過的實驗包括額外的學科書、去蟲的治療宣導、金錢誘因施予等給學生有顯著進步的老師作運用。當然Kremer在實驗過程也遇到了挫折：比如額外的教科書並沒有帶來學習上的助益。學生健康指數增加帶來出席率增加，但是並不意味他們有學得多（多到而促進經濟潛力增加)

Abhijit Banerjee, Esther Duflo是麻省理工學院的教授夫妻檔，則在Kremer的基礎上作研究。Ms Duflo是諾貝爾講歷年來最年輕的得主，也是最年輕的女性得主。兩位大部份的起始研究範圍是和Kremer同樣的出發點，「貧窮經濟學」但是針對的是偏向城市的貧困居民，而且有和總體數據作對照。兩位的研究地是印度，研究的成果和心得正好和2006年諾貝爾和平獎「微型金融學」的Muhammad Yunus意見相左。

三位在印度的研究，從窮人相關的事物著手，教師和護士的翹班率、疫苗計劃施行情形、公共設施管理情形，使用生產力大增的媒介物，比如施肥的採用造成什麼結果。他們不眠不休的研究統計數據找出因果，並從世界上無數種（無數原因造成的）貧困線上掙扎的窮人「學習」，並作為給國際性跨國企業的提醒或警惕。畢竟普世價值沒有死角，也不應該有任何例外。研究中的問題，可作為往後類似跨國研究的啟示，包括是否本來被說是外部因子的，作出了增長或萎縮的貢獻或敗軍之役，或是該因子為附隨的「外溢效應」或「無關而同時發生的背景」。

這篇經濟學者雜誌的作者很有趣，拿「By breaking big questions into smaller ones, and tackling each in carefully designed experiments.」，最貼切的翻譯是「大大的事情小小作，小小的事情好好作」。筆者有一次去東森購物的台北車站營業處，一出電梯的門口(東森電視新聞旁邊的大樓)，就是貼這兩排門聯，據說是王令麟和林青蓉的座右銘。這三位學者的實驗數據積少成多，分門別類後就成為了歸納的依據。「外部效力」問題仍然是作此類的田野實驗(圈出一批人當作追縱對象)，所常遇到的問題。不僅因果關係有時莫衷一是。經濟學者的作者真是感慨：People are complex, and the world ever-changing; thus it is hard to be confident that a relationship between two variables will endure. 白話來翻是人很複雜，世界常變動，因此很難說得準於兩個變數是否很牢靠固定的關係存在。翻譯起來就是名句：人生不相見，動如參與商。「自然」的觀察很難再有重覆性的、可以用因果闡述的事件，而給定條件的「田野實驗法」(Field Experiment)則可得到有意義的結論及理性公式。諾貝爾獎委員會的確很讚賞三位的務實作法。

Free exchange

A Nobel economics prize goes to pioneers in understanding poverty

Randomised trials help policymakers grasp which policies work and which don’t

Print edition | Finance and economics

Oct 17th 2019

THE MOST important question in economics is also the hardest: why do some countries stay poor while others grow rich? In 2015, 10% of the world’s population lived on less than $1.90 per day, down from 36% in 1990. But more than 700m people remain in extreme poverty, and the number grows every day in certain parts of the world, in particular sub-Saharan Africa. For their contributions to understanding gaps in development, the better to close them, Abhijit Banerjee, Esther Duflo and Michael Kremer have been awarded this year’s Nobel prize for economics. All three are Americans, though Mr Banerjee and Ms Duflo are immigrants (and married to each other). Ms Duflo is only the second woman to have received the prize and, at 46, the youngest winner ever.

Thirty years ago, economists mostly looked at the big picture. They studied large-scale structural transformations: from rural and agricultural to urban and industrial. Macroeconomists built growth theories around variables such as human capital, then ran cross-country growth regressions to try to measure relationships—for example, between years of schooling and GDP per person. But data were scarce or poor, and the vast number of potentially relevant factors made it hard to be sure what caused what.

In the mid-1990s Mr Kremer, at Harvard University, tried something different. With collaborators and co-authors, he began studying poverty with methods more commonly associated with chemists and biologists: randomised trials. If human capital—health, education, skills and so forth—is essential for development, then economists had better make sure they understand where it comes from. In Kenya he conducted field experiments in which schools were randomly divided into groups, some subject to a policy intervention and others not. He tested, among other things, additional textbooks, deworming treatments and financial incentives for teachers linked to their pupils’ progress.

Each such experiment shed a little light on one small part of the “hardest question”. Educational resources—textbooks, say—turned out to do little for learning outcomes. Making pupils healthier improved their attendance, but did not necessarily mean they learned more. The experiments had a larger result, however: they taught the economics profession that randomised trials could work in the field.

Mr Banerjee and Ms Duflo built on the foundation Mr Kremer laid, deploying randomised trials to study health care and entrepreneurship as well as education. In India, they found that focusing extra teaching resources on pupils who had fallen behind paid big dividends. They showed that microloans—small-scale lending to the cash-strapped poor—were less transformative than had been claimed, but could help ambitious entrepreneurs. The three scholars have studied absenteeism among teachers and nurses, immunisation programmes, the management of public infrastructure and the use of productivity-boosting technologies such as fertiliser. They have spent countless hours observing and learning from the daily struggles of the world’s poor.

By breaking big questions into smaller ones, and tackling each in carefully designed experiments, they overcame some hard epistemological problems. Economists who used cross-country regressions could not easily say whether extra schooling boosted growth or merely occurred alongside it. Field experiments, by contrast, could show not only the link between better teaching and greater learning, but how the connection worked.

There remained the problem of “external validity”: the extent to which a measured relationship holds outside the research context. People are complex, and the world ever-changing; thus it is hard to be confident that a relationship between two variables will endure. Researchers must also be aware that the groups being tested may differ subtly from a broader population, or that something in the experiment may be influencing participants’ behaviour. In mastering field research, Mr Banerjee and Ms Duflo showed how to overcome these difficulties. “Natural” experiments, such as an oil shock, cannot be rerun to satisfy nagging doubts. Field experiments can be replicated. Structuring experiments so that they can be scaled up over time permits greater confidence still.

A developing story

Each nugget of truth prised out of the data generated by field experiments represents a contribution to understanding the world. The hope is that many small truths can be piled together to make a big one. These laureates’ work uses economic theory as a guide, but nonetheless represents a departure from the discipline’s business-as-usual, in which economists peer down from on high at society and seek to discover the equivalent of Newton’s laws of motion. Randomised trials are a part of an important development in recent decades, away from high theory and towards an empirical grounding. With these awards the Nobel committee endorsed this shift. It is, furthermore, a practical award, celebrating work that offers ways to improve lives.

But the hardest question still looms. Mr Banerjee and Ms Duflo reckon that their work builds toward an answer. Taken together, their experiments reveal that the gap in productivity between the most and least efficient producers is much wider in developing economies than in advanced ones. Fix that, one small intervention at a time, and perhaps eventually the hard question will go away. More macro-minded economists counter that the huge fall in global poverty of the past three decades owes little to such fiddling. It happened, rather, as a confluence of global forces buoyed poor countries’ fortunes. The mystery of global poverty remains. If enough economists emulate the innovative spirit and scholarly care of this year’s laureates, it will not remain for ever. ■

Listen to our interview with this years economics Nobel laureates at economist.com/economicsnobel2019

This article appeared in the Finance and economics section of the print edition under the headline "Rich economics"

以下是筆者覺得寫得不錯的兩篇說明，一篇是天下雜誌內文(圖片省略，原文在https://www.cw.com.tw/article/article.action?id=5097228)，另一篇是

人為何貧窮？2019諾貝爾經濟學獎得主對打2006諾貝爾和平獎

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人為何貧窮？2019諾貝爾經濟學獎得主對打2006諾貝爾和平獎

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2019-10-14

2019諾貝爾經濟學獎頒給了研究貧窮議題的印度裔美國經濟學家巴納吉（Abhijit Banerjee）、法國經濟學家杜芙若（Esther Duflo）、以及美國發展經濟學家克雷默（Michael Kremer）。他們的研究顛覆了許多人「理所當然」的思惟，包括2006和平獎得主尤努斯提出的微型銀行構想。