For as long as most people can remember, food has been getting cheaper and farming has been in decline. In 1974-2005 food prices on world markets fell by three-quarters in real terms. Food today is so cheap that the West is battling gluttony even as it scrapes piles of half-eaten leftovers into the bin. 

    That is why this year's price rise has been so extraordinary. Since the spring, wheat prices have doubled and almost every crop under the sun—maize, milk, oilseeds, you name it—is at or near a peak in nominal terms. The Economist's food-price index is higher today than at any time since it was created in 1845. Even in real terms, prices have jumped by 75% since 2005. No doubt farmers will meet higher prices with investment and more production, but dearer food is likely to persist for years. 

    But the rise in prices is also the self-inflicted result of America's reckless ethanol subsidies. This year biofuels will take a third of America's (record) maize harvest. That affects food markets directly: fill up an SUV's fuel tank with ethanol and you have used enough maize to feed a person for a year. And it affects them indirectly, as farmers switch to maize from other crops. The 30m tonnes of extra maize going to ethanol this year amounts to half the fall in the world's overall grain stocks. 

    大多數(shù)人仍能記得糧食越來越便宜，農(nóng)業(yè)一直在走下坡路。從1974年到2005年，世界市場上糧食的實價掉了四分之三。今天的糧食是如此便宜以至于西方一邊反對暴飲暴食，一邊將成堆的只吃了一半的剩菜剩飯扔進垃圾箱。 

    這就是為什么今年的價格上漲如此的異乎尋常。自從今年春天小麥的價格已經(jīng)翻番，玉米、牛奶、油菜籽等幾乎所有陽光下的作物的牌價都在或接近最高點。《經(jīng)濟學家》的糧食價格指數(shù)已經(jīng)高于自該指數(shù)1845年創(chuàng)立以來的任何時候。自2005年以來，糧食的實價也已經(jīng)上升了75%。毫無疑問，隨著糧價的上升，農(nóng)民會增加投資，產(chǎn)量也會提高。高糧價可能會持續(xù)幾年。

    糧價的上升也是美國對乙醇燃料不計后果地實行補貼所帶來的自作自受的后果。今年生物燃料將消耗美國創(chuàng)紀錄的玉米收成的三分之一。這直接影響了糧食市場：用乙醇裝滿一輛越野車的油箱所消耗的玉米足夠一個人吃一年。間接的影響是，因為農(nóng)民不種其他作物而轉(zhuǎn)向種植玉米了。今年有三千萬噸額外的玉米用于制造乙醇，這占據(jù)了世界總體谷物儲存下降數(shù)的一半。