"Your money or your life." The choice traditionally presented by the highwayman is supposed to have only one sensible answer. Money is, after all, no use to a corpse. Yet economists often study something rather like the highwayman's offer in an attempt to uncover the answer to an important question: how much is your life actually worth? 

    Like many awkward questions, this is one that has to be answered. Safety regulations save lives but also raise the cost of doing business, a cost we all pay through higher prices. Are they worth it? Our taxes pay for life-saving spending on road safety and fire fighting. Are they high enough, or too high? 

    So how much are we willing to spend to save a life? A traditional planner's approach used to be to measure the value of wages lost due to death or injury. That's dreadful: it confuses what I think my life is worth with what my boss thinks my life is worth. 

    So an alternative is to ask people how much they would pay for a safer car or kitchen cleaner. But such surveys do not always produce sensible results. Our answers depend on whether we're being offered a safer ?10 household cleaner and then asked if we want the more dangerous ?5 version, or whether we're offered the ?5 brand and then asked if we'll pay ?10 for the safer product. People often answer ”no” to both questions, contradicting themselves. These inconsistencies mean that we're either irrational or lying to pollsters, and perhaps both. 

    Economists therefore tend to prefer observing real choices. If you're willing to cross a busy street to pick up a ?20 note, the economist who put it there can infer something about your willingness to accept risk. More orthodox approaches look at career choices: if you're willing to be a lumberjack, part of that decision is to accept risk in exchange for financial reward. 

    Being a soldier is risky; so is being a drug-dealer or prostitute. The difficulty, evidently, is to disentangle the health risk and the financial reward from all the other motivations to choose a particular way of life. That isn't easy but economists try. 

    World Bank economist Paul Gertler and his colleagues reckoned that Mexican prostitutes valued their lives at about $50,000 per year, based on willingness to take money not to use condoms. At five times their annual earnings, that's a similar figure to workers accepting risky jobs in rich countries. 

    There are anomalies. Steve Freakonomics Levitt and sociologist Sudhir Venkatesh calculated that Chicago drug dealers seemed to value their entire lives at $50,000 to $100,000 - low indeed, even for poor young men whose career choice indicates a taste for risks. 

    Whatever the frailties of these calculations, they are the best we have. And far from cheapening life, this sort of research often highlights just how valuable our safer, healthier modern lives really are. Kevin Murphy of the Chicago Graduate School of Business recently visited London to present his research on the value of health improvements in the US since 1970. They're vast - about $10 trillion in today's money. Looking further back, if you had to choose between the material progress of the 20th century and the improvements in health, it would be a toss-up. The health gains are as valuable as everything else put together. Encouragingly, health in most developing countries has improved faster than in rich ones, suggesting that global inequality is falling. 

    And a more personal piece of good news: Murphy reckons the delicious cheeseburger I ate before interviewing him only cost me ?1 worth of health. Talk about a good deal. 

    “要錢還是要命。”這個通常由劫匪提出的選擇，理應只有唯一明智的答案。畢竟，錢對死人來說是沒用的。然而，經濟學家們經常研究一些與劫匪的提議非常相似的東西，以揭示一個重要問題的答案：你的生命到底值多少錢？ 

    與許多棘手的問題一樣，這是個必須回答的問題。安全規章能夠拯救生命，但也會提高經營成本，而這是一個我們通過更高的價格、都需要支付的成本。它們真的物有所值嗎？在道路安全和消防安全方面，我們繳納的稅款，用作了拯救生命的支出。它們是否足夠高，或者是過于高昂了呢？
    那么，為了拯救一條生命，我們愿意花費多少呢？一種傳統計劃者的方法，曾是衡量死亡或受傷所導致工資損失的價值。這十分可怕：它混淆了我心目中自己生命的價值，與我老板心目中我生命的價值。 

    因此，另外一種選擇，就是詢問人們愿意為安全程度更高的汽車或廚房洗潔精支付多少錢。但是，這種調查并不總能得出明智的結論。我們的回答取決于，是否為我們提供了一種更為安全的、價值10英鎊的家用洗潔精，然后問我們是否想要一個更為危險的、價值5英鎊的產品；或者，是否向我們提供了售價5英鎊的品牌，然后問我們是否將為更安全的產品支付10英鎊。人們對上述兩個問題的回答往往都是“不”，這使他們自相矛盾。這些矛盾意味著，我們要么是缺乏理性，要么是在對調查者撒謊，或者兩者兼而有之。 

    因此，經濟學家們往往更愿意去觀察真實的選擇。如果你愿意橫穿一條繁忙的街道，去撿一張20英鎊的紙幣，把錢放在那里的經濟學家可推斷出一些與你承受風險的意愿有關的東西。更為正統的方法著眼于職業選擇：如果你愿意當一名伐木工人，這個決定的一部分，便是承受風險，以此換取金錢上的回報。 

    當兵很危險；販毒或當妓女也很危險。顯然，難點在于，從所有其它選擇特定生活方式的動機中，將健康方面的風險和金錢上的回報區別開來。這并不容易，但經濟學家正在進行嘗試。 

    世界銀行(World Bank)經濟學家保羅•格特勒(Paul Gertler)和他的同事們估計，墨西哥妓女對其生命的估價為每年5萬美元，其依據是她們愿意為了錢而不使用安全套。這個數目是其年收入的5倍，比例與富裕國家承受危險工作的工人相仿。 

    也有一些異常情況存在。《魔鬼經濟學》(Freakonomics)作者史蒂文•萊維特(Steven Levitt)和社會學家素德赫•文卡特斯赫(Sudhir Venkatesh)計算，芝加哥的毒販對其整個生命的估值介于5萬美元至10萬美元。事實上這很低，即便對于職業選擇有風險偏好的貧窮年輕人來說也是如此。 

    不管這些計算存在何種缺陷，它們都是我們所擁有的最佳方法。這遠非貶低生命的價值，此類研究往往突顯出，我們的更安全、健康的現代生活，到底有多么珍貴。芝加哥大學商學院(Chicago Graduate School of Business)的凱文•墨菲(Kevin Murphy)最近訪問了倫敦，展示他目前的研究，課題是美國1970年后醫療保健改善的價值。這一價值非常巨大，以目前的貨幣計算，大約為10萬億美元。回顧更久遠的歲月，如果你必須在20世紀物質方面的進步，和醫療保健方面的改善中進行選擇，這實在是難以取舍。醫療保健方面的收獲，與其它所有進步的總和一樣珍貴。令人鼓舞的是，在多數發展中國家，醫療保健改善的速度比富裕國家更快，表明全球不平等正在縮小。 

    對我自己來說，一個好消息是：墨菲計算，我采訪他之前吃的那個美味奶酪漢堡包，只讓我損失了價值1英鎊的健康。這是筆很劃算的交易。