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In developed countries today life expectancy at birth is about 80 years. That figure has almost doubled over the past century. Life expectancy at birth measures how long someone born today would survive if the patterns of mortality existing when they were born continued through their lifetime. But they will not. 在发达国家，现在出生的人预期寿命约为80岁。这个数字在过去的1个世纪里几乎翻了一番。人在出生时的预期寿命衡量的是，现在出生的人，如果他们出生时整个社会的死亡率模式在他们一生中保持不变，那么他们的寿命是多久。但死亡率模式不会保持不变。 These patterns improve, so that most people born in the past century have lived far beyond their life expectancy at birth. Children born today can expect to live well beyond 80 years, even if the claim by Peter Thiel and Aubrey de Grey that the first 1,000-year man is already alive is optimistic. 死亡率模式在不断改善，因此，过去一个世纪中出生的大部分人活着的时间，已经远远超出了他们出生时的预期寿命。即便企业家彼得•蒂尔(Peter Thiel)和学者奥布里•德格雷(Aubrey de Grey)宣称第1个能活到1000岁的人已经出现的说法过于乐观，但可以预计，今天出生的儿童的寿命将远不止80岁。 Life expectancy was much lower a century ago because many children died in infancy and many adults failed to achieve a normal lifespan because they were killed by now-curable infectious diseases. Deaths from these sources are now so low that even dramatic further improvements will not have much effect on average lifespan. The most important factor today is increases in life expectancy after conventional ages of retirement. This measure has recently been improving at one to two months a year. | 
