During the past half-century, whenever America'sunemployment rate has risen by half a percentage point or more the NBER haslater (often much later) declared it a recession.

在过去的半个世纪，只要当美国的失业率上升0.5或者更多的百分点，NBER随后（经常要更久）就宣布美国经济进入衰退。