In state firms, party committees once controlled workers' lives, monitoring everything from their ideological rectitude to their reproductive cycle.

ECONOMIST: The long arm of the state

For example, one way to track the reproductive cycle in a female is to follow the waxing and waning of sex hormones.

ECONOMIST: Endangered species

By 40, a woman's reproductive chance is less than 5% per cycle, so a natural pregnancy is rare.

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