But these stages are meant to describe the typical life cycle of a modern American family.

但这些阶段旨在描述现代美国家庭的典型生命周期。

I suggest, however, that there are certain definite reasons why, in the case of a typical industrial trade cycle in the nineteenth-century environment, fluctuations in the marginal efficiency of capital should have had cyclical characteristics.

然而，我认为，在 19 世纪典型的工业贸易周期的情况下，资本边际效率的波动应该具有周期性特征，这是有某些明确原因的。