Amid the hubbub over a few less-bad-than-expected statistics, America’s economic debate has turned to the nature of the recovery. Optimists expect a vigorous rebound as confidence returns, pent-up demand is unleashed and massive government stimulus takes effect. Most observers are bracing for a long slog, as debt-laden consumers rebuilt their savings, output growth remains weak and unemployment continues to rise. There is, however, something that eventually will have a much bigger impact on Americans’ prosperity than the slope of the recovery. That is the effect of the crisis on America’s potential rate of growth itself.

An economy’s long-term speed limit ( its “trend ”or “potential” rate of growth ) is the pace at which GDP can expand without affecting unemployment and, hence, inflation. It is determined by growth in the supply of labor along with the speed with which productivity improves. The pace of potential growth helps determine the sustainability of everything from public debt to the prices of shares. Unfortunately, the outlook for America’s potential growth rate was darkening long before the financial crisis hit. The IT-induced productivity revolution, which sent potential output soaring at the end of the 1990s, has waned. More important, America’s labor supply is growing more slowly as the population ages, the share of women working has leveled off and that of students who work has fallen.

由于一小部分經(jīng)濟數(shù)據(jù)顯示當前經(jīng)濟狀況并沒有預期的那樣壞，一些人就騷動起來，開始討論起美國經(jīng)濟的復蘇之路。樂觀人士認為在信心恢復、壓抑已久的內(nèi)需得到釋放和大量的政府刺激計劃奏效的背景下，將會有一個強勢的反彈。大多數(shù)專家，正準備迎來一個更加漫長的艱難之旅：債務累累的消費者正在重建他們的積蓄，產(chǎn)量的增長依舊遲緩，失業(yè)率仍在攀升……但是，還有一個比復蘇趨勢更會影響美國繁榮的東西，那就是這次危機給美國潛在的經(jīng)濟增長所帶來的不良影響。

一個經(jīng)濟體長期處在最高的增長速度，是以GDP的增長不被失業(yè)率和通貨膨脹所影響為條件的。而這，決定于勞動力供應的增長和生產(chǎn)力發(fā)展的速度。潛在增長的速度幫助決定了從國債到股價這一切能否持續(xù)穩(wěn)定。遺憾的是，在金融危機發(fā)生很久以前，美國經(jīng)濟潛在增長率的前景就十分暗淡。IT行業(yè)引發(fā)的生產(chǎn)力革命，曾在上世紀90年代末使產(chǎn)量大幅上漲，但衰敗了。更重要的是，美國勞動力供給的增長速度正變得比人口老齡化速度慢，女性工作者的比例已經(jīng)穩(wěn)定，學生的已經(jīng)下降。