美国经济很快将不能从有利的贸易数据中获得增长动力了。

　　美国商务部（Commerce Department）将于周三上午公布6月份贸易数据。经济学家们估计，美国6月份的贸易逆差将从5月份的260亿美元增加到287亿美元，这主要是受石油进口价格不断增长的推动。

　　虽然这仍远低于上年同期602亿美元的贸易逆差，但却标志着过去四个月中有三个月贸易逆差出现了增长。这更加证实了许多经济学家早前的怀疑，即去年秋季以来美国贸易逆差迅速收窄的局面已经结束。

　　进口石油的价格在去年夏天不断下跌之后，最近一直在持续上涨。更重要的是，有迹象显示，占美国进口商品大多数的非石油产品进口，在经历了一段时间的下跌后已经触底。去年秋天美国经济形势恶化导致进口量下降。

　　大和证券美国公司（Daiwa Securities Americas）的首席经济学家墨兰（Michael Moran）将财政部的关税数据视为一个反映美国非石油产品进口情况的不太理想指标。他说，这一数据经季节性因素调整后6月份增长了6.4%，这暗示非石油产品的进口也在逐渐增加。

　　随着美国企业重建被消化的库存以及美国消费者支出的触底，美国对非石油类进口产品的需求应不断增长。

　　虽然这表明美国经济状况在改善，但也意味着最近几个季度推动国内生产总值（GDP）增长的一个主要动力将不复存在。

　　贸易逆差缩小有利于GDP的增长，因为这意味着美国的出口增速快于进口增速。

　　自从本轮经济衰退开始以来，对外贸易一直对美国的GDP起着巨大的推升作用。有两个季度，外贸因素甚至使美国GDP实现了正增长。而在其他几个季度，对外贸易也减轻了美国GDP的恶化程度。以今年第一季度为例，虽然美国的GDP下降了6.4%，但如果没有对外贸易的贡献，GDP降幅会达到9%.

　　如果消费者和企业的乐观情绪上升导致美国贸易逆差增加，短期而言是个好迹象。

　　但美国经济的长期健康则有赖于消费者放弃过度举债和过度消费的生活方式，正是美国人的这种生活方式导致美国贸易逆差增大。

　　The U.S. economy soon will need to move ahead without help from favorable trade data.

　　The Commerce Department releases June trade data Wednesday morning. Economists estimate the U.S. trade deficit widened to $28.7 billion from $26 billion in May， driven largely by the rising price of imported oil.

　　Such a gap would still be much narrower than the $60.2 billion deficit a year earlier. But it would mark the third time in the past four months that the deficit has widened， and it would add to many economists' sneaking suspicions that the rapid diminution of the trade gap since last fall has ended.

　　The price of imported oil has been rising lately after falling last summer. More important， there are signs that nonpetroleum imports —— the bulk of trade —— may have bottomed after sinking when the economy worsened last fall.

　　Michael Moran， chief economist at Daiwa Securities Americas， watches Treasury Department customs duties as an imperfect gauge of nonpetroleum imports. They rose by a seasonally adjusted 6.4% in June， according to Mr. Moran， suggesting nonpetroleum imports edged higher as well.

　　As U.S. businesses rebuild spent inventories and as consumer spending finds a floor， demand for nonpetroleum imports should keep rising.

　　That signals a healthier economy， but will mean that a major prop for gross domestic product in recent quarters will go away.

　　In the accounting of GDP， a shrinking trade gap bolsters growth because foreign customers are buying what the U.S. makes at a faster rate than Americans are buying foreign-made stuff.

　　Since the recession began， trade's contribution to overall GDP has been huge. In two quarters， it was big enough to turn GDP positive. In most other quarters， it kept a bad GDP print from being much worse. In the first quarter， for example， GDP fell 6.4%， but would have been down 9% without the benefit of trade.

　　If a wider trade gap is driven by consumers and businesses feeling friskier， that is a good sign for the short term.

　　The economy's long-term health， however， depends on consumers resisting the excessive borrowing-and-spending ways that widened the trade gap in the first place.