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经济概念的一个月。上周，金融市场体验了上世纪70年代时的感受，美国通胀率与失业率的双重上升，唤起了人们对那个时代的糟糕回忆：十年滞胀，让战后的黄金岁月和凯恩斯共识就此终结。然后，本周又有报道称，联合国世界粮食计划署(UN World Food Programme)可能不得不对粮食援助实行配额制。在全球食品价格不断上涨的背景下（全球食品价格已较2000年的低位上涨75%以上，仅2007年一年的升幅就超过20%），这则消息唤醒了人们早年的恐惧，召回了托马斯•马尔萨斯牧师(Reverend Thomas Malthus)的幽灵。

    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. 

    飙升的食品价格也令人想起了距今更近的一些担忧。今年1月，随着食品价格上涨18%，中国折合成年率的通胀水平达到11年高点，中国观察家们不禁回想到1988年的食品价格上涨，以及随后的社会动荡、抗议浪潮和民心不安。人们通常认为，通胀是造成1989年大规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. 

    这种价格上涨是供需两方面趋势的结果。在需求方面，关键因素在于新兴市场消费的强劲增长——这些国家收入的大幅增加推动了消费的增长。以中国为例，过去十年，在全球大豆和肉类消费增长中，中国所占的比例达到40%。与此同时，在关键的大宗商品市场上，干旱和疾病等因素造成的一系列供应方面的中断也发挥了作用。

    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.

    也许，过去一年价格上涨的最大推动力量是全球能源市场的发展。高油价鼓励了集中发展生物燃料的政策，包括提供大量慷慨的财政支持。生产方面也迅速对这些激励措施做出了反应：世界银行(World Bank)的报告显示，美国已经将20%的玉米产量用于生物燃料，欧盟用于生物燃料的植物油产量达到68%。用途上的变化推动了价格的上扬，减少了这些农作物的粮食供应，鼓励了其他农业用地从粮食生产转向生物燃料生产。

    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.

    马尔萨斯关于全球食品短缺的幽灵追随着世界经济的发展，这在现代经济史上不是第一次。上世纪70年代以及90年代中期食品价格的飙升，都曾向世人发出警告：农业产能无法跟上世界人口的增长。随着供给作出反应，每一次价格的跃升都是暂时的。人们有充分的理由相信：最近这一轮市场失衡最终会以同样的方式得到解决。但即便如此，针对对当前环境如此乐观的解读，我还是要提出两项重要告诫。

    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，面对价格上涨的刺激，供给方面的反应可能会比前几次更为滞后，因为当前世界能源市场的变化，以及由此产生的相关生物燃料需求，可能会持续相当长一段时间。由于气候变化和环境恶化威胁到几个关键地区的农业产能，过去供给反应的弹性，可能无法很好地体现未来的状况。

    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，在供给长期滞后于需求期间，可能存在巨大的社会与经济成本。有3方面特别值得注意。

    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，食品价格长期处于高位，对许多世界上最贫困的人口和最贫穷的经济体将是一个噩耗。尽管在美国等富裕国家的消费篮子中，食品所占比例相对较小，仅为10%左右，但中国的平均水平约为30%，而撒哈拉以南非洲国家则超过了60%。最容易受到伤害的国家是那些低收入的食品净进口国。食品价格的上涨，会给通常已经不堪油价上涨重荷的进口账单带来更大压力。有几个最贫穷经济体就属于这一类，它们严重依赖于食品援助来满足自身需要。但过去20年，全球这类援助的数量一直没有增加。更糟糕的是，鉴于很大一部分援助由每年固定数额的美元构成，随着价格上涨，派发的援助数量也会呈现下降趋势。

    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，各国需要应对重要的社会压力。一些新兴市场已经在疲于应付不平等现象加剧带来的后果，对这些市场而言，应对重要的社会压力可能就会更成问题。就算食品价格上涨是一把双刃剑——因为农业收入增加会缩小城乡收入差距，但受害最深的困难是城市贫困人口，通常是政治不稳定的团体，而许多农村贫困人口同样也会受累。

    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，食品价格上涨会要求各国收紧货币政策。鉴于食品在消费篮子中所占比例的差异，以及富国央行往往不把食品价格纳入核心通胀指标的事实，发展中国家经济体可能会做出更大的政策反应。各国政府也许还会考虑采取价格管制和其他直接措施。然而，富国央行也会不得不密切关注从紧货币政策可能对非食品价格产生的溢出效应。