2011年5月16日 星期一

A spoonful of medicine...

A spoonful of medicine...

Should economics be more like medicine? I don't mean that economists should be more like doctors – I've met a few doctors – but that economists should learn from the relationship that medical practice has with medical evidence.


Medicine, like economics, deals with complex systems that are still not well understood; like economics, it has its share of quacks; but unlike economics, medicine has swallowed many of its ethical qualms about running controlled experiments in difficult circumstances.


Randomised controlled trials are now catching on in economics, especially development economics. (Such a trial would involve, for instance, approving loans to a randomly chosen subset of loan applicants.) Two new books, Poor Economics and More Than Good Intentions, each by leading practitioners of randomised trials, explain the consequent discoveries.

隨機對照實驗如今在經濟學領域很流行,特別是發展經濟學。 (例如,這種實驗可能涉及批准向隨機選取的貸款申請者發放貸款。)兩本新書——《貧窮 (可能誤譯) 經濟學》(Poor Economics)和More Than Good Intentions的作者都是隨機實驗的領先實踐者,書中對隨後的發現進行了解釋。

Clearly such trials have their limits, but I'ma big fan of the approach. However, it would be a great shame if economists learned nothing more from doctors than to use randomisation.


One lesson that has emerged all too slowly from medical practice is the need for trial registries, in which researchers give notice that a clinical trial is about to begin, noting exactly what they will do.


Trial registries sound like a pernickety piece of bureaucracy. In fact, they could hardly be more important. When analysing any statistical finding, researchers must allow that sometimes remarkable patterns emerge by chance. Imagine that there are 20 researchers, each investigating whether mint humbugs cure cancer. Purely by happenstance, we'd expect one of the researchers to find evidence that they do. She'll approach a medical journal and get her fascinating results published. The other 19 researchers may not bother at all – or, realising that their research is destined to be published in The Journal of Uninteresting Results, they will drag their heels.

實驗註冊聽上去像一種麻煩的官僚作風。實際上,它們極為重要。在分析數據發現時,研究人員必須承認,不尋常的模式有時會意外出現。假設有20名研究人員,各自都在調查薄荷硬糖能否治愈癌症。純粹出於意外,我們預計有一位研究人員發現了肯定的證據。她會接洽醫學雜誌,將吸引人的結果公之於眾。另外19名研究人員可能會毫不介意,或者,如果意識到他們的研究注定將在《無趣結果雜誌》(The Journal of Uninteresting Results)上發表,他們會不合作。

In short, published research is systematically biased in favour of striking results that may be coincidence. The trial registry matters because later researchers into the anti-carcinogenic properties of humbugs can take all the non-results into account.


Dean Karlan, a Yale economist, co-author of More Than Good Intentions, and founder of Innovations for Poverty Action, which co-ordinates and evaluates development projects in poor countries, argues that trial registries are harder to design in social science than in medicine . Researchers cannot control a project as tightly as clinicians can – they may find that the project they are evaluating is changed halfway through.

耶魯大學(Yale)經濟學家迪恩•卡蘭(Dean Karlan)辯稱,社會科學領域的實驗註冊比醫學領域更難設計。研究人員對項目的控制無法像臨床醫師那樣嚴格,他們可能會發現,他們正在評測的項目在中途就發生了變化。卡蘭是More Than Good Intentions一書的聯席作者,Innovations for Poverty Action的創始人——該公司與貧窮國家合作,對這些國家的開發項目進行評估。

High-quality empirical research is not just a matter of using tools such as randomised trials and trial registries – it's about the entire research culture. A simple example: if academic careers are in thrall to the number of articles published in the top journals, and if the top journals are not interested in publishing boring-sounding replications of earlier research, then these replications will not be attempted. Yet replication is a foundation of experimental science.


Professor ​​Jonathan Shepherd, a clinician at Cardiff University, points out that the culture of evidence permeates medicine. Doctors are trained in university hospitals; their professors are themselves practising doctors, and their research agenda is driven by their needs as medical practitioners.

卡迪夫大學(Cardiff University)臨床教授喬納森•謝潑德(Jonathan Shepherd)指出,證據文化滲透整個醫學界。醫生在醫學院接受培訓;他們的教授本身就是行醫的醫生,他們的研究日程受到他們作為行醫者需要的推動。

Meanwhile their pupils, thoroughly indoctrinated as to the value of medical evidence, read about new research in the British Medical Journal every week. In short, in medicine, academic evidence and everyday practice are intertwined. No doubt this symbiotic relationship is less than perfect in the real world; nevertheless it is something economists would do well to emulate.

同時,他們的學生被徹底灌輸了醫學證據的價值,他們每週都會閱讀《英國醫學雜誌》(British Medical Journal)上發表新的研究。簡而言之,在醫學領域,學術證據和日常實踐交織在一起。毫無疑問,這種共生關係在真實世界里遠沒有那麼完美;然而,經濟學家最好能效仿一下。

Tim Harford's latest book is 'Dear Undercover Economist' (Little, Brown)

本文作者的新書是《親愛的臥底經濟學家》(Dear Undercover Economist),Little, Brown出版社出版