In some respects they were incredibly productive years, particularly from the perspective of his writing.

从某些方面来说，那是令人难以置信的富有成效的岁月，特别是从他的写作的角度来看。

The earth's population has doubled since 1960, and with more than a billion young people just entering their productive years.

自 1960 年以来，地球人口翻了一番，并且有超过 10 亿的年轻人刚刚进入生产年龄。