Even in cultures without access to mass media, the optimum waist-to-hip ratio for women is around 0.7, which corresponds most closely to an hourglass shape, and is linked to fertility.

即使在和大众传媒没有交集的文化中，女性腰围与臀围的最佳比例也是在0.7左右，近似于沙漏形状，并与生育有关。

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When fertility is high and a country is young (median age below 20), there are huge numbers of children and the overall dependency ratio is high.

一个国家生育率高，表示这个国家很年轻（中位年龄在20岁以下），小孩数量庞大，依赖性比例相当高；

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Scientists concluded that such a small ratio was considered good for a woman's health and resulted in high fertility.

科学家总结认为这样的比例对女性健康和生育有利。

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Today, as Japan has aged and fertility has declined, the ratio is three to one.

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For all developed countries, high life expectancy is also associated with below-replacement fertility, which reduces the ratio of workers to retirees.

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Already, several European nations have fertility rates even more modest than Japan's (though they still have a lower ratio of elderly, due to shorter life spans).

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