美国经济乏善可陈，导致上周高盛(Goldman Sachs)经济学家们一个月内第二次调低了美国经济增长的预期，并警告称“我们已经预见到了这一预测走低的风险”。

    高盛最新预计2季度美国经济将以3%的速度蹒跚前行，低于三周前预测的3.5%和年初预测的4%。该公司同时预计4月份美国新增就业机会仅为15万个——低于3月份的24.4万个，也显著低于CNNMoney预测的17.8个。

    高盛经济学家扎克•庞德尔概括常见因素认为，诸多因素导致了本轮经济增速放缓，其中包括高油价、日本大地震对制造业生产的冲击及其他各种临时性因素(如美国南方的龙卷风和国防支出的减少)。

    但他同时表示，仅凭这些因素很难解释本应相当强劲的经济复苏为何如此疲弱。所有迹象都表明本轮增速放缓将是深层次的，而不是暂时性的。

    “某些特定因素看来确实重要，但不能完全解释近期数据的弱势，美国经济增速看来的确已放缓，”庞德尔在上周五致客户的一份报告中写道，“我们同样感到不解，因为2010年底时让我们看到希望的很多趋势——包括私营经济减债所取得的进展、更宽松的信贷和金融环境以及改善的劳动市场——现在并没有改变。”

    庞德尔指出，通过跟踪新订单、销售和发货量、就业、材料价格和库存制定的高盛分析师指数已跌至2010年春季放缓以来的新低；2010年春季的放缓直到美联储(Fed)承诺将通过所谓二次量化宽松政策的美国国债购买方案提升经济活力才结束。也许你认为美联储要结束量化宽松政策存在难度，持这种观点的大有人在。

    高盛绝非近来唯一发出此类论调的公司。美国银行美林(Bank of America Merrill Lynch)的经济学家们上周也将2季度美国经济增长率预测值调低至了2%，并警告称接踵而至的“黯淡”数据看来不太可能戛然而止。

    高盛去年底一度非常乐观，如今却公然下调前景，透露出一丝不祥之兆——而且，有充分的理由相信还将有更多的坏消息传来。说不准哪一天，本•伯南克就会碰到大麻烦。

    “如果未来几个月数据仍然不见改善，”庞德尔说，“我们可能需要考虑进一步下调美国经济增长率预测值。”

    So lukewarm that economists at Goldman Sachs last week cut their economic growth forecast for the second time in a month, only to warn a few days later that "we already see downside risk to that

    Goldman now sees the U.S. economy struggling to limp forth at a 3% pace in the second quarter, down from 3.5% just three weeks ago and 4% at the start of the year. The firm expects the economy to have added just 150,000 jobs in April – down from 244,000 in March and well below the 178,000 CNNMoney forecast.

    Economist Zach Pandl rounds up the usual suspects, blaming high oil prices, manufacturing disruptions triggered by the earthquake in Japan and various other temporary factors (such as tornadoes in the South and a drop in defense spending).

    But those alone can hardly account for all the slack in what was supposed to be a reasonably vigorous recovery by now, he says. All signs point toward a broad-based slowdown, rather than one tied to temporary factors.

    "Special factors do seem important, but they cannot explain all the recent weakness in the data, and the economy does seem to have slowed," Pandl writes in a note to clients Friday. "We are somewhat puzzled by this because many of the trends that made us more optimistic around yearend 2010—progress in private sector deleveraging, easier credit and financial conditions, and an improving labor market—are still in place."

    Pandl notes that the firm's analyst index – which tracks new orders, sales and shipments, employment, materials prices and inventories – has fallen to levels last seen during the spring 2010 slowdown that ended only when the Fed promised to stoke up activity with the bond-buying plan dubbed QE2. If you think the Fed is going to have trouble walking away from quantitative easing, you aren't alone.

    Goldman is hardly the only firm to be humming this tune lately. Economists at Bank of America Merrill Lynch last week cut their second-quarter growth forecast to 2%, warning that a run of "dreary" data doesn't seem likely to end suddenly.

    But Goldman was so bullish at the end of last year that a pronounced darkening in its outlook is ominous – and there is every reason to believe the bad news isn't over. Another day, another giant problem for Ben Bernanke.

    "If the data flow fails to improve in coming months," says Pandl, "we may need to consider a further downgrade to our US growth forecasts."