Has the Rate of Investment Fallen?
发现美国非住宅净投资率在1960年代末至1970年代末下降了近40%，其中五分之四源于折旧率上升，五分之一源于总投资率下降，并分析了折旧率上升的原因。
Although the ratio of gross fixed nonresidential investment to GNP has decreased very little since the late 1960rs, the corresponding net investment ratio declined by nearly 40 percent between the second half of the 1960's and the second half of the 1970's. Four-fifths of this decline was due to the increased ratio of depreciation to GNP and only one-fifth to the decreased ratio of gross investment to GNP. The increased ratio of depreciation to GNP was in turn due in equal amounts to the higher ratio of capital to GNP and to the higher rate of depreciation. Nearly half of the higher depreciation rate was due to the increased rate of depreciation of equipment and nearly half to the increased share of equipment in the capital stock.