translation.en: And an amazing fact for techno-optimists is that in the first half of the 20th century, the rate of improvement of life expectancy was three times faster than it was in the second half of the 19th century.
translation.zh: 还有一个让技术乐观主义者高兴的事实： 在20世纪前半期， 人类寿命的增长速度 是19世纪后半期 寿命增长速度的三倍。