American exports are rising at the most rapid rate in decades, helped by a weaker dollar and by rising prices of food sent overseas. The trade figures for June, released this week, showed that the dollar value of total exports was running at a pace 19.2 per cent higher than it was last year. Not since 1988, another year when exports were helped by a falling dollar, have exports grown so quickly.Those figures are not adjusted for inflation, and the real increase is undoubtedly smaller given the rapid rise in the price of grains. But the increase is nonetheless substantial. American imports are also growing, however, despite expectations that the weakening American economy would slow them down. Expressed in dollars, imports in the three months till June were 14.1 per cent higher than in the same period of 2007, and trade deficit was 6.6 per cent higher.Nonetheless, there are signs of a slowing economy in the figures. Exports to Brazil were up 43 per cent, while those to Argentina leaped 65 per cent and Colombian exports climbed 42 per cent. But exports to Venezuela climbed just 10 per cent. Exports to Asia tended to rise slower than exports to most of the world. Those to China — the largest customer for American goods after Canada and Mexico — rose almost 18 per cent. That move reflects the power of a weak currency to make exports more competitive. In 2001 and 2002, when a dollar was worth more than a euro, American exports to countries in the euro zone were falling. By June, however, two euros could buy three dollars.