中國經濟必然"有升必有降"

What would China look like if it were growing at just 2 per cent a year? That sounds like a ridiculously pessimistic question given China’s performance in the past three decades. Certainly, it has manifold problems. Indeed, its economy is already slowing. But what misadventure could possibly bring its growth rate crashing down so spectacularly?

如果中國經濟年增長率僅爲2%，那將是怎樣的情形？鑑於中國在過去30年的表現，這聽起來像是一個悲觀到荒謬程度的問題。當然，中國存在多方面的問題。事實上，中國經濟已開始放緩。但是，什麼樣的災難纔可能把中國增速拉到如此慘不忍睹的地步呢？

That is the wrong question, according to an influential paper by US economists Lant Pritchett and Lawrence Summers . For them, “the single most robust and striking fact” about growth is “regression to the mean” of about 2 per cent. Only rarely in modern history, they say, have countries grown at “super-rapid” rates above 6 per cent for much more than a decade. China has managed to buck the trend since 1977 by harnessing market forces, engineering possibly the longest spell “in the history of mankind”. But what goes up, the authors tell us, must eventually come down.

根據美國經濟學家蘭特•普里切特(Lant Pritchett)和勞倫斯•薩默斯(Lawrence Summers)的一份頗有影響力的論文，這是一個錯誤的問題。在他們看來，有關增長的“唯一最強大和驚人的事實”是“迴歸（約2%的）均值”。他們說，在現代歷史上，只在極少的情況下，國家才能將超過6%的“超高速”增長維持10年以上。而自1977年以來，中國通過調動市場力量突破了這個慣常趨勢，締造了“人類歷史上”可能最長的高速增長期。但這兩位作者告訴我們，有升必有降。

They have trawled through the data and drawn two powerful conclusions. One is that there is almost no statistical basis for predicting growth from one decade to another. Extrapolation is a mug’s game – or, as they put it, “current growth has very little predictive power”. From 1967 to 1980, Brazil grew at an average annual rate of 5.2 per cent. Few would have predicted, then, that for the next 22 years per capita income would grow at precisely zero.

他們在梳理數據之後，得出兩條強大的結論。其一是，通過一個十年預測下一個十年的增長，幾乎沒有統計學基礎。外推法是一種傻瓜遊戲——或者如他們所言，“目前的增長對預測未來幾乎毫無作用”。從1967年到1980年，巴西的年均增長率爲5.2%。當時很少有人會預測，在接下來22年巴西人均收入增長率將恰好爲零。

Their second finding is that episodes of super-rapid growth last a median of nine years. China is the big exception. The only countries with fast-growth episodes that come close are Taiwan and South Korea, which managed 32 and 29 years respectively. According to the authors, once such episodes end, the median drop in growth is 4.65 points. That would cut China’s growth to 4 per cent and India’s to 1.6 per cent – far lower than almost anyone is predicting.

他們的第二項發現是，超高速增長期的平均長度是9年。中國大陸是一個很大的例外。唯有臺灣和韓國的表現與其接近，它們的高速增長期分別爲32年和29年。兩位作者表示，一旦這樣的增長期結束，增長率降幅的均值是4.65個百分點。按此計算，中國的經濟增長率將降至4%，印度將降至1.6%——遠低於幾乎所有人的預測。

The thesis has huge potential ramifications, both economic and geopolitical. If China and India continue their current growth trajectories, their combined gross domestic product will rise to $66tn by 2033, against $11tn today. If they regressed fully to mean, they would reach a combined GDP of just $24tn. The authors have no need to explain why China’s, or indeed India’s, growth should fall so precipitously. This is just what happens. Their reasoning puts the onus on optimists to explain otherwise.

該文可能具有重要的經濟和地緣政治意義。如果中國和印度保持目前的增長軌跡，到2033年其國內生產總值(GDP)之和將從目前的11萬億美元，上升至66萬億美元。如果完全迴歸均值增速，到時中印GDP之和僅能達到24萬億美元。兩位作者沒有必要解釋中國或（實際上）印度的增速爲何應會如此陡峭下降。這不過就是目前發生的事情。他們的步步分析使得解釋怎樣才能不發生這種情況成爲樂觀者的責任。

There are several conceivable rejoinders. The first applies to emerging markets generally. The idea of “convergence” holds that poor countries can grow faster than rich ones. That is partly because there is low-hanging fruit; for example, moving people from unproductive rural jobs to more productive urban ones. Poor countries can also copy rich ones; they do not have to reinvent the wheel. Niall Ferguson, professor of history at Harvard University, refers to “six killer apps of prosperity”: competition, scientific revolution, property rights, medicine, consumer society and the work ethic. Since we already know what they are, they can be “downloaded”. Several Asian economies, including Japan, Taiwan, South Korea and Singapore have more or less caught up with western living standards. If they can do it, why not others? Regression to mean, however, implies that such speedy catch-up is impossible, or at least very difficult.

有幾種可以想象到的反駁理由。第一個適用於新興市場的總體狀況。“趨同”理念認爲，貧窮國家可以比富國增長得更快。這部分是因爲“低懸的果實”；例如，把人們從生產率低的農村工作，轉向生產率更高的城市工作。窮國也可以學習模仿富國；它們不必重新發明輪子。哈佛大學(Harvard)歷史學教授尼爾•弗格森(Niall Ferguson)提到了“繁榮的6大殺手級應用”：競爭、科學革命、財產權、醫學、消費社會和職業道德。既然我們已知道它們是什麼，就可以“下載”它們。包括日本、臺灣、韓國和新加坡在內，幾個亞洲經濟體的生活水平或多或少都趕上了西方。如果它們能做到，爲什麼其他經濟體不能？然而，迴歸均值意味着，如此迅速的追趕是不可能的，或者至少是非常困難的。

Is there anything about China specifically that suggests it could buck the trend? First, it has already done so, growing rapidly for more than 30 years. The two economists say this makes a rapid slowdown more likely. But perhaps it is the reverse. Chinese leaders may have learnt how to beat the odds. Second, as Jim O’Neill, who coined the term Brics, says, the authors’ data may be skewed by the mostly disappointing economies of Latin America, the Middle East and Africa. Perhaps Asian economies have discovered a secret sauce. Third, China’s long-lived expansion follows many decades of chaos and suboptimal growth. What we are seeing now could plausibly be a long-pent-up recovery – the country’s own regression to mean. Fourth, China’s size could confer growth-sustaining advantages in terms of economies of scale and size of domestic market. If true, that would also apply to India.

中國有沒有什麼特定因素表明它能夠逆勢而上？首先，中國已經做到了這一點，快速增長期超過了30年。兩位經濟學家說，這使得快速放緩的可能性變得更大。但也許會出現相反情況。中國領導人可能已經學會了如何戰勝命運。第二，“金磚國家”(Brics)一詞的發明者吉姆•奧尼爾(Jim O'Neill)說，兩位作者的數據可能由於拉美、中東和非洲這些最令人失望的經濟體而有所偏差。或許，亞洲經濟體已經發現了一種獨家祕方。第三，在中國的長期增長之前，是幾十年的混亂和低水平增長。我們現在看到的，很可能真是一種被長期壓抑之後的復甦——這是中國自己的迴歸均值過程。第四，中國的體量可能產生規模經濟和國內市場規模方面的維持增長的優勢。如果此情屬實，這也適用於印度。

The authors do offer one reason for believing China’s growth rate is unsustainable: “institutional inadequacies”, particularly the failure to control corruption. To some, the argument is an old saw dressed up in new data: the country cannot keep growing because it is not democratic. Still, the regression to mean theory provides a powerful corrective to mechanical extrapolation. The authors are right. Any time you hear the words, “based on current growth trends”, you should pause for thought.

兩位作者確實提出了一個認爲中國增長速度不可持續的理由：“體制不健全”，尤其是未能控制腐敗。有些人認爲，此觀點是披着新數據外衣的陳詞濫調：因爲不是民主體制，所以該國不能保持增長。不過，迴歸均值理論對機械推論提供了一種強有力的糾正。作者在這一點上是正確的。只要你聽到“基於目前的增長趨勢”的說法，你都應該停下來想一想。