[author]蒂姆·哈福德
[content]
托馬斯.謝林與 “統(tǒng)計學意義上的生命價值”
*蒂姆·哈福德（Tim Harford）
英國《金融時報》的經(jīng)濟學專欄作家
編者按
2020年4月3日“金融時報”發(fā)表從“統(tǒng)計學意義上的生命價值”看當前防控新冠疫情的如下文章。該文作者Tim Harford追溯了2005年諾貝爾經(jīng)濟學獎得主托馬斯.謝林1968年首次提出這個概念的背景。1948年正式成立的蘭德公司從美國國防部接受的第一個研究項目是用運籌學設(shè)計對蘇聯(lián)的核轟炸方案。但蘭德設(shè)計出的方案被國防部拒絕了。原因是國防部很多官員是飛行員出身，不能接受蘭德公司方案中把飛行員的“生命價值”設(shè)定為零。從1948年到1968年的20年間，蘭德公司的研究人員對飛行員的“生命價值”多次重新估算，例如從飛行員培訓成本定為27萬美元，但從飛行員緊急跳傘的彈出系統(tǒng)設(shè)計成本來倒推，飛行員的“生命價值”在100萬和900萬美元之間 （ Tim Harford此文又基于“統(tǒng)計學意義上生命價值概念的冷戰(zhàn)起源”一文，參見：
https://www.aeaweb.org/articles?id=10.1257/jep.28.4.213）
托馬斯.謝林1968年“你救的生命可能是你自己的”(“The Life You Save May Be Your Own”)一文（見謝林文集“選擇與后果”）的革命性意義在于指出蘭德公司“生命價值”概念的錯誤。謝林認為，研究人員和政策制定者沒有能力和權(quán)利判定其他人的“生命價值”，而應(yīng)該在“社會成本-收益”分析中以當事人（如飛行員）本身的風險偏好為基礎(chǔ)。1963年，謝林指導一位前飛行員Jack Carlson寫作博士論文。
Carlson發(fā)現(xiàn)（通過訪談和從實際行為倒推），飛行員在和平時期愿意多承擔0.00232%的死亡風險以換取增加2280美元的年收入。Carlson沒有進一步用2280除以0.00232%得出491萬美元的飛行員自身的“生命價值”估計。但5年后的1968年，謝林深化了Carlson這一觀察，提出了基于當事人自身的“統(tǒng)計學意義上的生命價值”概念。目前，很多國家的政府在公共政策制定中必須進行“社會成本-收益分析”，都要運用謝林的“統(tǒng)計學意義上的生命價值”概念。例如，美國環(huán)境署把“統(tǒng)計學意義上的生命價值”定為1000萬美元（https://www.epa.gov/environmental-economics/mortality-risk-valuation#whatvalue）。
Tim Harford此文據(jù)此估算，花費10萬美元去防止新冠肺炎感染一個人，從“社會成本-收益分析”的角度是值得的?！皩嶒炛髁x治理”公號第195期曾介紹“謝林圖示”對于研究社會合作機制的重要作用，希望本期公號有助于讀者進一步了解謝林思想在當前全球抗疫斗爭中的意義。如果讀者想對“社會成本-收益分析”中的“統(tǒng)計學意義上的生命價值”進行深入研究，可參考哈佛大學法學院桑斯坦教授2018年出版的 “成本收益革命“一書第三章。
How do we value a statistical life?
It is clear that we should be willing to pay huge costs to save lives from Covid-19
TIM HARFORD
https://www.ft.com/content/e00120a2-74cd-11ea-ad98-044200cb277f
The coronavirus lockdown is saving lives but destroying livelihoods. Is it worth it? I’ve been accused of ignoring its costs. For an economist, this is fighting talk. Love us or hate us, thinking about uncomfortable trade-offs is what we economists do.
Three points should be obvious. First, we need an exit strategy from the lockdowns — a better strategy than President Donald Trump’s, “One day it’s like a miracle, it will disappear.” Expanding emergency capacity, discovering better treatments, testing for infection and testing for antibodies could all be part of the solution, along with a vaccine in the longer term.
Second, the economic costs of any lockdown need to be compared with the costs of alternative policies, rather than the unachievable benchmark of a world in which the virus had never existed.
Third, the worth of a human life is not up for discussion. This week I lost a mentor of unlimited kindness. As I write these words I hear that a beloved family member is also reaching the end of her remarkable journey. Their lives, like the life of any individual, were priceless.
Yet no matter how much we want to turn our gaze away from the question, it hangs there insistently: is this all worth it?
We spend money to save lives all the time — by building fire stations, imposing safety regulations and subsidising medical research. There is always a point at which we decide we have spent enough. We don’t like to think about that, but better to think than to act thoughtlessly. So what are we willing to sacrifice, economically, to save a life?
A 1950 study for the US Air Force ducked this question, recommending a suicidal military strategy that valued pilots’ lives at precisely zero. Other early attempts valued lives by the loss of earnings that an early death would cause — effectively making retired people worthless, and the death of a child costly only if the child could not be replaced by a new baby.
The late Thomas Schelling, a Nobel Prize-winning economist, mocked these errors as he imagined the death of a family breadwinner like himself: “His family will miss him, and it will miss his earnings. We do not know which of the two in the end it will miss most, and if he died recently this is a disagreeable time to inquire.”
There must be a better way to weigh the choices that must be weighed. But how?
Schelling suggested focusing not on the value of life, but on the value of averting deaths — of reducing risks. A life may be priceless, but our actions tell us that a statistical life is not.
The engineer Ronald Howard has proposed a convenient unit, the “micromort” — a one-in-a-million risk of death. Implicitly, we constantly weigh up small risks of death and decide if they are worth it. Despite inconsistencies and blind spots in our behaviour, we value reducing risks to our own lives very highly, but not infinitely so.
We vote for governments that hold our lives in similarly high regard. For example, the US Environmental Protection Agency values a statistical life at $10m in today’s money, or $10 per micromort averted. I have seen lower numbers, and higher.
I am giving most of my figures as conveniently round numbers — there is too much uncertainty about Covid-19 to be more precise. But if we presume that 1 per cent of infections are fatal, then it is a 10,000 micromort condition. Being infected is 100 times more dangerous than giving birth, or as perilous as travelling two and a half times around the world on a motorbike. For an elderly or vulnerable person, it is much more risky than that. At the EPA’s $10 per micromort, it would be worth spending $100,000 to prevent a single infection with Covid-19.
You don’t need a complex epidemiological model to predict that if we take no serious steps to halt the spread of the virus, more than half the world is likely to contract it. That suggests 2m US deaths and 500,000 in Britain — assuming, again, a 1 per cent fatality rate.
If an economic lockdown in the US saves most of these lives, and costs less than $20tn, then it would seem to be value for money. (By way of comparison, each 20 per cent loss of gross domestic product for a quarter represents a cost of about $1tn.) One could quibble with every step of this calculation. Perhaps some of those who die were so ill that they would have died of other causes within days. Perhaps Covid-19 is not quite so dangerous. Yet it is clear that with so many lives at stake, we should be willing to pay huge costs to protect them.
We must remember something else: the risk of being wrong. We will inevitably make mistakes. The measures we take to contain coronavirus might do more damage to people’s livelihoods than necessary. Or we might allow the virus too much leeway, needlessly ending lives. In a spreading pandemic, the second mistake is much harder to repair than the first.
Fighting this virus demands economic sacrifices: not without limit; and not without end. But if not now, then when?
轉(zhuǎn)載自 實驗主義治理 公眾號