由于美国推出的“旧车换现金”计划提振了消费支出，而美国制造商也在增加生产，经济学家们对美国今年下半年的经济增长情况做出了更为乐观的预期。

　　在美国政府上周公布了第二季度国内生产总值（GDP）数据后，经济学家们纷纷开始修正自己对美国经济增长情况的预期。数据显示，美国经济今年第二季度较上年同期下降1%，降幅低于预期。上调对未来经济增长预期的势头本周仍在持续，因为人们认为美国政府的汽车销售刺激计划有望在未来几个月增加消费者支出，并迫使汽车制造商较原计划生产更多新车。

　　美国商务部（Commerce Department）周二宣布，6月份的消费者支出增长了0.4%.但经通货膨胀因素调整后，当月的消费者支出为下降0.1%.6月份的个人收入也下降了1.3%，创出四年来的最大单月降幅。

　　这一数据显示，由于就业市场疲软，美国消费者今年上半年承受了很大压力。这种状况暗示，人们期待中的GDP增长将不足以明显降低失业率。

　　不过现在出现了本轮金融危机开始以来最大一波上调GDP预测值的浪潮。瑞银（UBS AG）现在预计，美国经济第三季度将增长2.5%，高于此前预计的2%，第四季度将增长3%，高于此前预计的2.5%.富国银行（Wells Fargo & Co.）也将它对美国第三季度经济增长率的预测值从2.2%上调至3%.它还将美国第四季度经济增长率预测值从1.6%上调到2.0%.T. Rowe Price Group Inc.则将它对美国第三季度经济增长率的预测值从1.3%上调到2.75%.

　　经济学家们此前已经预计，随着企业在今年上半年逐步消化库存，美国的经济增长率未来几个月将出现反弹。本周一份令人鼓舞的制造业报告显示，受这一预期推动，美国的新订单和工业生产都出现了跃升。

　　穆迪经济网（Moody's Economy.com）的首席经济学家赞迪（Mark Zandi）说，库存减少和销售增加这两个因素结合在一起，构成了人们至少对今年下半年的经济增长抱更乐观看法的基本理由。该公司将它对美国今年第三季度经济增长率的预测值从1.1%上调到1.6%，将其对第四季度经济增长率的预测值从0.2%上调到了2.1%.

　　富国银行的高级经济学家魏特纳（Mark Vitner）说，如果美国国会批准将政府对“旧车换现金”计划的补贴增加20亿美元，汽车销售甚至可能进一步提振消费者支出。但这也有可能导致美国的个人储蓄率再次下降。美国6月份的储蓄率已由前月的6.2%下降至4.6%.

　　不过，MFR Inc.的首席经济学家夏皮罗（Joshua Shapiro）则认为，一旦美国消费者不是在从政府的刺激计划中获得好处，美国的消费基本面仍会非常严峻。夏皮罗原本预计，美国经济今年第三季度将增长0.2%，第四季度为零增长，但他现在预计下半年的经济增长率有可能达到2%.

　　在“旧车换现金”计划停止实施后，美国消费者有可能再度抑制支出，而长期来看美国的储蓄率预计会继续攀升。

　　美国经济持续增长的最理想情况是，经济在下半年表现强劲，消费者支出和消费者信心增加，而没有再出现这次经济衰退以来的大规模裁员。否则的话，经济要继续增长，就必须借助企业投资的回升。虽然新订单数据正在显示令人鼓舞的迹象，但目前还没有什么迹象显示经济的各个领域已普遍出现了增长。

　　虽然人们并不认为住房市场会带动经济复苏，但这一领域的改善迹象却有可能推动经济增长。美国全国地产经纪商协会（National Association of Realtors ）周二宣布，用以衡量购房签约情况并预测成屋销售情况的成屋待完成销售指数今年6月上升3.6%，达到94.6点，为2007年6月以来的最高点位。这一指数暗示，成屋销售情况未来一到两个月预计会出现改善。不过，该指数最近一直不大能准确预示成屋销售的实际情况。

　　Economists are predicting a brighter second half of the year as the cash-for-clunkers program boosts spending and U.S. manufacturers ramp up their production.

　　Revisions began after last week's gross-domestic-product report， showing the economy contracted at a better-than-expected 1%. This week， the upward revisions have continued on hopes the government's auto stimulus program would propel consumer spending in coming months and force auto makers to make more new cars than previously planned.

　　Meanwhile， the Commerce Department said Tuesday that consumer spending rose 0.4% in June. But adjusted for inflation， it fell 0.1%. Personal-income data also fell 1.3% in June， the largest single-month drop in four years.

　　The data indicated that consumers concluded the first half under intense pressure from a weak labor market. That suggests the anticipated GDP growth won't be enough to substantially bring down the unemployment rate.

　　Still， in the largest wave of upward revisions of GDP forecasts since the financial crisis began， UBS AG is now predicting 2.5% growth in the third quarter， up from 2%， and 3% growth in the fourth quarter， up from 2.5%. Wells Fargo & Co. also revised its third-quarter forecast to 3% growth， up from 2.2%. For the fourth quarter， it is now predicting 2.0%， up from 1.6%. T. Rowe Price Group Inc. increased its third-quarter projection to 2.75% from 1.3%.

　　Economists already had expected growth to rebound in coming months after companies drew down inventories in the first half of the year. A promising manufacturing report this week showed a jump in new orders and production， building on those expectations.

　　'When you combine leaner inventories with more sales， that's the fundamental reason for being more optimistic about at least the second half of this year，' said Mark Zandi， chief economist for Moody's Economy.com. The firm revised its third-quarter forecast to 1.6% from 1.1%， and its fourth-quarter outlook to 2.1% from 0.2%.

　　If the cash-for-clunkers program receives an additional $2 billion in funding from Congress， sales could boost consumer spending even further， said Mark Vitner， a senior economist at Wells Fargo. It would likely cause another drop in the personal savings rate， which fell to 4.6% in June from 6.2% a month earlier.

　　However， MFR Inc. chief economist Joshua Shapiro said， 'The underlying fundamentals for the consumer are going to remain pretty tough' once they aren't benefiting from government programs. Mr. Shapiro originally predicted 0.2% growth in the third quarter and no growth in the fourth quarter， but said now 2% growth is likely in the second half.

　　When the cash-for-clunkers program expires， consumers are likely to rein in spending once again， and the savings rate is expected to continue its climb in the long run.

　　The best-case scenario for sustained growth is a strong second half， with improved consumer spending and confidence， and without the massive layoffs that have marked much of the recession. Short of that， business investment would have to make a comeback for expansion to continue. New orders are showing encouraging signs， but so far there's little sign the growth is widespread.

　　Although housing isn't expected to lead the recovery， signs of improvement in the sector could buoy growth in the economy. The pending home-sales index， which measures housing contract activity and is designed to foreshadow existing home sales， increased 3.6% in June to 94.6 —— its highest point since June 2007， the National Association of Realtors said Tuesday. The measure suggests that existing home sales are likely to rise in the next month or two， though the relationship between the two indicators has been volatile lately.