統計不應成爲政治的奴婢
As he appeals to the British public to vote him in as prime minister, the leader of the opposition proposes collecting new data to provide a better picture of how the country is doing. “Wellbeing can’t be measured by money or traded in markets,” he says. He adds, “We measure all kinds of things but the only thing we don’t measure is the thing that matters most.”
當他呼籲英國公衆投票選他當首相時，反對黨領導人提議收集新數據，以便更好地瞭解英國的國情。“福祉無法用金錢衡量，也不能在市場上交易，”他說。他補充說，“我們衡量各種各樣的事物，但唯一沒有衡量的是那最重要的東西。”
All of the preceding paragraph is true, except for one detail: the first quotation is from David Cameron, then leader of the opposition, in 2006. The second is from Ed Miliband, the current leader of the opposition, a couple of weeks ago. Both men are united, it seems, by a feeling that the most familiar economic measuring stick, GDP (Gross Domestic Product), just isn’t up to the job. Cameron wanted to gather data on wellbeing or happiness; Miliband wants a “cost of living” index. Few reasonable people can object to gathering timely and authoritative economic and social statistics, yet Miliband and Cameron have managed the impressive feat of being cynical and naive at the same time.
上述段落的所有內容都是真實的，只有一個細節例外：第一個引語是2006年戴維•卡梅倫(David Cameron)所說，當時他是反對黨領袖。第二個是現任反對黨領導人埃德•米利班德(Ed Miliband)幾個星期前所講。兩人看起來都有一種相同的感覺：人們最熟悉的經濟衡量標尺國民生產總值(GDP)已經不合用。卡梅倫要收集關於福祉或幸福的數據；米利班德想要一個“生活成本”指數。沒有多少理性的人反對收集及時、權威的經濟和社會統計數據，但米利班德和卡梅倫兩人做到了不容易的事，那就是表現得既犬儒又幼稚。The cynical motives in both cases are plain enough — as were, for example, Nicolas Sarkozy’s when, as French president, he commissioned some alternative economic measures that just happened to be more flattering to France. As the leader of a party with a reputation for liking free markets and low taxes, Cameron wanted to soften his image and suggest a broader, more caring perspective. Miliband is trying to replace a government that is presiding over a sudden uptick in GDP, so naturally he wishes to point the spotlight somewhere else.
這兩種情況下的犬儒動機是顯而易見的——就像尼古拉•薩科齊(Nicolas Sarkozy)還是法國總統的時候那樣，他委託出爐了一些另類的經濟衡量指標，而這些指標恰好展現法國的長處。作爲以崇尚自由市場和低稅收出名的保守黨的領導人，卡梅倫希望軟化自己的形象，暗示一種更包容更關愛的視角。米利班德正試圖取代一個成功推動英國GDP突然出現起色的政府，因此，他很自然地想把聚光燈投射到別的地方。
The naivety requires more statistical digging to uncover, and it’s in three parts. The first point is that many of these data already exist. The Office for National Statistics asks questions about wellbeing as part of the Labour Force Survey. The ONS also publishes regular data on inflation, while wage data are in the Annual Survey of Hours and Earnings. Neither Cameron nor Miliband was really asking the statisticians at the ONS to do something new, just to do it more often or in more detail.
揭露幼稚的一面需要挖掘更多統計數據，這需要分爲三部分。第一點是，許多此類數據早已存在。英國國家統計局(ONS)在勞動力調查(Labour Force Survey)中問到有關福祉的問題。該局也定期發佈通脹數據，而工資數據包含在工時和薪資年度調查(Annual Survey of Hours and Earnings)中。卡梅倫和米利班德並非真的要求國家統計局的統計學家拿出新花樣，而只是希望統計的次數更頻繁或者內容更加詳細。The second point is that no mainstream politician has ever regarded GDP (or its cousin Gross National Product) as the only worthwhile policy objective, although we are often invited to draw that conclusion. Robert Kennedy’s famous complaint that GNP counts “napalm” and “nuclear warheads” but not “the health of our children” or “the strength of our marriages” was wonderful rhetoric — but surely nobody believes that if only the statisticians had collected different data, divorce would be prevented and the Vietnam war would never have happened.
第二點是，從來沒有主流政治人物將GDP（或者國民生產總值(GNP)）作爲唯一有價值的政策目標，儘管我們經常容易得出這一結論。羅伯特•肯尼迪(Robert Kennedy)曾經說，GNP計入了“凝固汽油彈”和“核彈頭”，卻沒有包括“我們孩子的健康”或者“我們婚姻的力量”；他的這一著名抱怨雖言辭美妙，但誰能相信只要統計學家收集了不同的數據，離婚就可以被阻止，而越南戰爭就永遠不會發生呢？An acerbic comment in Nature last year complained that, “Despite the destruction wrought by the Deepwater Horizon oil spill in 2010 and Hurricane Sandy in 2012, both events boosted US GDP because they stimulated rebuilding.” But this is only a problem if the Deepwater Horizon spill was in some way caused by the collection of GDP data.
去年，《自然》(Nature)雜誌上的一個尖刻評論抱怨道：“雖然2010年‘深水地平線’(Deepwater Horizon)石油泄漏和2012年颶風桑迪(Hurricane Sandy)造成了巨大破壞，但這兩個事件提振了美國GDP，因爲它們刺激了重建工作。”但是，只有在“深水地平線”石油泄漏是GDP數據收集以某種方式所導致的情況下，這纔是一個問題。If politicians truly sought to maximise GDP they would immediately abolish all planning restrictions, all barriers to immigration and a good chunk of the welfare state. These ideas are political suicide, which proves that GDP is not the sole objective of public policy — it’s just a way to try to measure the size of the economy.
如果政客們真的試圖使GDP最大化，他們就會立即廢除所有的市政規劃限制、廢除所有移民障礙以及福利國家制度的一大部分。這些構想等於政治自殺，這證明了GDP不是公共政策的唯一目標，而只是一種衡量經濟規模的方法。The deepest piece of naivety is the idea that — in Ed Miliband’s words — we can measure the one single “thing that matters most”. ONS data on median wages are a case in point. According to one measure, the median wage for people in full-time employment rose just 0.1 per cent in the past tax year — well below the rate of inflation. According to another way of calculating exactly the same number, median wages rose by 4.1 per cent, well above the rate of inflation. (The median is the wage earned by someone slap in the middle of the sample.)
最深層的幼稚是這樣的想法：（用米利班德的話說）我們可以衡量一件“最重要的東西”。國家統計局關於中位數工資的數據是一個很好的例子。根據一項衡量指標，全職就業人士的中位數工資在上一個納稅年度僅上漲0.1%，遠低於通脹率。而以完全相同數字爲依據的另一種計算方法顯示，中位數工資增長了4.1%，遠高於通脹率。(中位數工資是指樣本里處於中間位置者的收入)。How can that be? The lower measure is the median for the entire sample. The higher measure looks at the median wage of people who’ve been in the same job for the entire year — the vast majority. The two numbers would differ if — for example — some high-income people retired and some low-income people joined the labour force (school-leavers? immigrants?). It’s possible for most people to enjoy a decent pay rise while median wages stagnate, and that may be what is happening now. One rather narrow question — “how are things going for people in full-time employment in the middle of the income distribution?” — turns out to have two very different answers. Each one is perfectly justifiable.
怎麼會這樣呢？較低的測量結果是整個樣本的中位數。較高的測量結果針對全年都做同一份工作的人（絕大多數人）的中位數工資。例如，如果一些高收入者退休了，而一些低收入者加入了勞動力大軍（中學畢業生？移民？），這兩個數字就會有所不同。大多數人享受體面的加薪而中位數工資保持不變的情況是可能發生的，而這可能是現在正在發生的。換句話說，一個相當狹義的問題——“處於收入分配中間位置的全職工作者的境遇如何?”——結果有兩個非常不同的答案，而每一個都有無懈可擊的依據。We haven’t even got into questions of part-timers, the self-employed, the poorest, the richest, pensioners or benefit recipients. The idea that we can somehow measure “the thing that matters most” is quite absurd.
我們甚至還沒有涉及關於兼職者、自由職業者、最貧困人口、最富有的人、養老金領取者或福利領取者的問題。那種認爲我們能夠以某種方式衡量“最重要的東西”的想法是很荒謬的。It’s the duty of our official statisticians to provide a range of timely and objective statistics that will lead to better decisions. That is why so many different types of data must be gathered, analysed and published. It is a hard job, which is why the ONS has better things to do than help our schoolboy politicians score points off each other.
官方統計學家有責任提供一系列及時客觀的統計數據，幫助制定出更好的決策。這就是爲什麼必須收集、分析併發布如此多不同類型的數據。這是一項艱苦的工作，也是爲什麼比起幫助幼稚的政客彼此壓倒對方，英國國家統計局還有更重要的事情要做。Tim Harford’s latest book, ‘The Undercover Economist Strikes Back’, is now available in paperback. Twitter: @TimHarford
本文作者蒂姆•哈福德(Tim Harford)的新書《臥底經濟學家反擊戰》(The Undercover Economist Strikes Back)的平裝本現已上市。Twitter:@TimHarford
