translation.en: But if growth slows down, instead of doubling our standard of living every generation, Americans in the future can't expect to be twice as well off as their parents, or even a quarter [more well off than] their parents.
translation.zh: 但如果经济增长速度减慢， 结果将不是生活水平比以前翻一番。 未来的美国人民不能期待生活水平比上一代好一倍， 或者只是好上四分之一。