Countries that do not have a well-functioning civil registration system only have approximate ideas of the Numbers, the longevity and the health of their population.

那些没有建立完善民事登记系统的国家对其人口的数量、寿命和健康状况，往往只有一些粗略的概念。

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It is estimated that anywhere from 50 to 100 million people were killed worldwide, or the approximate equivalent of one third of the population of Europe.

据估计全世界有50至100万人死于流感，或者说大约三分之一的欧洲人口。

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A simple (though approximate) model of population growth is the Malthusian growth model.

一个简单的(虽然近似)模型的人口增长率是马尔萨斯的增长模式。

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For example, they only used the scores of players between the ages of 17 and 25 as a way to approximate the current undergraduate population.

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More specifically, imagine the simplest case of a population of a constant size - say a million (the approximate size of the Holy Land at the time of Jesus).

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