来自《耶鲁大学开放课程：1600年后西方社会的流行病 第11集 第11集》

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  and it's often called his thesis-- where he was dealing
  他的论点经常被称为
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  with the demographic fact of
  当他在论述人口统计事实
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  what he called a mortality revolution;
  他所谓的死亡率革命时
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  a demographic transition in which cities,
  这是指一个城市在初期
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  for the first time, become places that are
  成为一个膨胀的区域
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  dependent for their expansion not only on inward migration
  而其膨胀不仅仅依赖于人口的内迁
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  to the towns, but on the fact that the longevity
  而且也依赖于其人口出生率超过死亡率
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  and the birthrate come to exceed the death rate;
  这一现象的持久性
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  which was something new, a real demographic revolution.
  这是一种新的现象 即所谓的人口革命
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  And why was this achieved?
  那么 这是怎么形成的呢
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  Many people have thought and postulated that it was due
  许多人都考虑过并假定为
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  to medical science, to conscious policy
  这现象应归功于医学科学 慎重的政策