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.