受感染的池塘，无论多大规格或放养多久的虾一般死亡率可达70%至80%。

Typical mortality in the affected ponds was 70% to 80%, and all ages and sizes of shrimp were affected.

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要是贺拉斯晚出生那么几年，他可以从美国人口普查局发现，秋天的人口死亡率一般低于冬、春两季。为什么呢？

Had he lived a little later, Horace might have found out from the U.S. Census Bureau that the death rate is usually lower in autumn than in winter and spring.

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当儿童死亡率下降时，夫妻终于少生孩子了——但是 这个过渡一般至少要经过一代人。

When childmortality declines, couples eventually have fewer children—but that transitionusually takes a generation at the very least.

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