the study of changes in the number of births, marriages, deaths, etc. in a particular area during a period of time

historical demography 历史人口统计学

The demography of an area is the number and characteristics of the people who live in an area, in relation to their age, sex, if they are married or not, etc.

The increase in the number of young people leaving to work in the cities has had a dramatic impact on the demography of the villages. 越来越多的年轻人到城市工作，这对乡村人口状况产生了巨大的影响。