February has been the month for revisiting old and unpleasant economic concepts. Last week, financial markets experienced that 1970s feeling, as a combination of rising inflation and unemployment in the US triggered unwelcome memories of the decade of stagflation that ended the postwar golden age and the Keynesian consensus. Then came this week's report that the United Nations' world food programme might have to ration food aid. Set against a backdrop of rising food prices worldwide – global food prices have now risen by more than 75 per cent since their lows of 2000, jumping more than 20 per cent in 2007 alone – the news revived fears from a much earlier era, conjuring up the Reverend Thomas Malthus. 

    今年2月成了反思那些令人不快的古老經濟概念的一個月。上周，金融市場體驗了上世紀70年代時的感受，美國通脹率與失業率的雙重上升，喚起了人們對那個時代的糟糕回憶：十年滯脹，讓戰后的黃金歲月和凱恩斯共識就此終結。然后，本周又有報道稱，聯合國世界糧食計劃署(UN World Food Programme)可能不得不對糧食援助實行配額制。在全球食品價格不斷上漲的背景下（全球食品價格已較2000年的低位上漲75%以上，僅2007年一年的升幅就超過20%），這則消息喚醒了人們早年的恐懼，召回了托馬斯•馬爾薩斯牧師(Reverend Thomas Malthus)的幽靈。

    Soaring food prices have also revived some more contemporary worries. When China's annual inflation rate spiked to an 11-year high in January on the back of an 18 per cent increase in food prices, China-watchers found themselves casting their minds back to the food price rises of 1988 and the social disturbances, protests and civil unrest that followed. Inflation is often cited as one of the factors behind the major demonstrations in 1989. 

    飆升的食品價格也令人想起了距今更近的一些擔憂。今年1月，隨著食品價格上漲18%，中國折合成年率的通脹水平達到11年高點，中國觀察家們不禁回想到1988年的食品價格上漲，以及隨后的社會動蕩、抗議浪潮和民心不安。人們通常認為，通脹是造成1989年大規模游行示威的原因之一。

    This rise in prices is a consequence of both demand and supply trends. On the demand side, the key factor has been the strong consumption growth in emerging markets, which in turn has been powered by those countries' impressive income gains. China, for example, has accounted for up to 40 per cent of the increase in global consumption of soyabeans and meat over the past decade. At the same time, a series of supply-side disruptions in key commodity markets ranging from drought to disease have been at work. 

    這種價格上漲是供需兩方面趨勢的結果。在需求方面，關鍵因素在于新興市場消費的強勁增長——這些國家收入的大幅增加推動了消費的增長。以中國為例，過去十年，在全球大豆和肉類消費增長中，中國所占的比例達到40%。與此同時，在關鍵的大宗商品市場上，干旱和疾病等因素造成的一系列供應方面的中斷也發揮了作用。

    Perhaps the most important drivers of price gains over the past year are developments in world energy markets. High oil prices have encouraged a policy focus on biofuels, including lashings of generous financial support. Production has responded quickly to these incentives: the World Bank reports that the US has used 20 per cent of its maize production for biofuels and the European Union 68 per cent of its vegetable oil production. This change in usage has boosted prices, reduced the supply of these crops available for food and encouraged the substitution of other agricultural land from food to biofuel production.

    也許，過去一年價格上漲的最大推動力量是全球能源市場的發展。高油價鼓勵了集中發展生物燃料的政策，包括提供大量慷慨的財政支持。生產方面也迅速對這些激勵措施做出了反應：世界銀行(World Bank)的報告顯示，美國已經將20%的玉米產量用于生物燃料，歐盟用于生物燃料的植物油產量達到68%。用途上的變化推動了價格的上揚，減少了這些農作物的糧食供應，鼓勵了其他農業用地從糧食生產轉向生物燃料生產。

    This is not the first time in modern economic history that the Malthusian spectre of global food shortages has stalked the world economy. Surges in food prices in the 1970s and then again in the mid-1990s both prompted warnings that agricultural capacity was failing to keep pace with a growing world population. Each time, the prices jumped it proved to be temporary as supply responded. There are good reasons for believing that this latest bout of market disequilibrium will ultimately reach the same resolution. That said, however, there are two important caveats to set against such an optimistic reading of current circumstances.

    馬爾薩斯關于全球食品短缺的幽靈追隨著世界經濟的發展，這在現代經濟史上不是第一次。上世紀70年代以及90年代中期食品價格的飆升，都曾向世人發出警告：農業產能無法跟上世界人口的增長。隨著供給作出反應，每一次價格的躍升都是暫時的。人們有充分的理由相信：最近這一輪市場失衡最終會以同樣的方式得到解決。但即便如此，針對對當前環境如此樂觀的解讀，我還是要提出兩項重要告誡。

    First, the lag in supply response to the stimulus provided by higher prices may prove to be of greater duration than its predecessors, to the extent that the current changes in world energy markets – and hence the associated demand for biofuels – are likely to be lasting ones. With climate change and environmental degradation threatening agricultural capacity in several key regions, the elasticity of past supply responses may prove to be a poor guide to the future.

    第一，面對價格上漲的刺激，供給方面的反應可能會比前幾次更為滯后，因為當前世界能源市場的變化，以及由此產生的相關生物燃料需求，可能會持續相當長一段時間。由于氣候變化和環境惡化威脅到幾個關鍵地區的農業產能，過去供給反應的彈性，可能無法很好地體現未來的狀況。

    Second, during the extended period in which supply continues to lag behind demand there are likely to be significant social and economic costs. Three in particular stand out. 

    第二，在供給長期滯后于需求期間，可能存在巨大的社會與經濟成本。有3方面特別值得注意。

    Most important, a period of protracted higher food prices will be bad news for many of the world's poorest people and its poorest economies. While the share of food in the consumption basket of a rich country such as the US is relatively low, at about 10 per cent, it averages about 30 per cent in China and more than 60 per cent in sub-Saharan Africa. Those countries that are most vulnerable are the low-income net food importers. Higher food prices add more strain to import bills that have often already been stretched by higher energy prices. Several of the poorest economies fall into this category and are heavily dependent on food aid to meet their needs. But the worldwide volume of such aid has stagnated for the past two decades and, what is worse, the quantity of aid delivered tends to fall as prices rise, given that a large proportion comprises a fixed annual dollar amount.

    最重要的是，食品價格長期處于高位，對許多世界上最貧困的人口和最貧窮的經濟體將是一個噩耗。盡管在美國等富裕國家的消費籃子中，食品所占比例相對較小，僅為10%左右，但中國的平均水平約為30%，而撒哈拉以南非洲國家則超過了60%。最容易受到傷害的國家是那些低收入的食品凈進口國。食品價格的上漲，會給通常已經不堪油價上漲重荷的進口賬單帶來更大壓力。有幾個最貧窮經濟體就屬于這一類，它們嚴重依賴于食品援助來滿足自身需要。但過去20年，全球這類援助的數量一直沒有增加。更糟糕的是，鑒于很大一部分援助由每年固定數額的美元構成，隨著價格上漲，派發的援助數量也會呈現下降趨勢。

    Next, there are important social strains to be managed. These may be particularly problematic for those emerging markets that are already struggling to deal with the consequences of growing inequality. Granted, higher food prices are something of a two-edged sword here, since higher agricultural earnings could reduce rural-urban income disparities. But the big losers are likely to be the urban poor, typically a politically volatile group, while many of the rural poor will also suffer.

    其次，各國需要應對重要的社會壓力。一些新興市場已經在疲于應付不平等現象加劇帶來的后果，對這些市場而言，應對重要的社會壓力可能就會更成問題。就算食品價格上漲是一把雙刃劍——因為農業收入增加會縮小城鄉收入差距，但受害最深的困難是城市貧困人口，通常是政治不穩定的團體，而許多農村貧困人口同樣也會受累。

    Finally, higher food prices will call for tighter monetary policy. Given the disparity in the share of food in consumption baskets, and the fact that rich country central banks tend to exclude food prices from their core inflation measures, the policy reaction will tend to be greater in developing economies. Authorities may also be tempted by price controls and other direct measures. However, rich country central banks will also have to keep a close watch on any spillover effects that tighter monetary policy could have on non-food prices.

    最后，食品價格上漲會要求各國收緊貨幣政策。鑒于食品在消費籃子中所占比例的差異，以及富國央行往往不把食品價格納入核心通脹指標的事實，發展中國家經濟體可能會做出更大的政策反應。各國政府也許還會考慮采取價格管制和其他直接措施。然而，富國央行也會不得不密切關注從緊貨幣政策可能對非食品價格產生的溢出效應。