And most of those slaves were African born, because the brutal living and working conditions prevented natural population growth.

这些奴隶中的大多数都是非洲出生的，因为残酷的生活和工作条件阻碍了人口的自然增长。

From a national perspective, the natural population growth rate in 2021 was 0.34 per thousand, which was declined by 1.11 per thousand than 2020, NBS data shows.

国家统计局数据显示，从全国来看，2021 年人口自然增长率为 0.34%.，比 2020 年下降 1.11%.。