1·By some studies, the safety nets for retirees have reduced fertility rates.
一些研究表明，退休人员的社会保障体系使生育率降低了。
2·To develop more accurate population forecasts, demographers have to know a great deal more than now about the social and economic determinants of fertility.
为了做出更准确的人口预测，人口统计学家必须比现在更多地了解生育率的社会和经济决定因素。
3·With its fertility artificially suppressed by the one-child policy, it is ageing at an unprecedented rate.
由于其生育率被独生子女政策人为地压低，它的老化速度也是史无前例的。
4·The link between living standards and fertility exists within countries, too.
国家内部的生活水平和生育率也存在联系。
5·The odd ones out are America and Britain, which both have lots of women at work and fertility rates close to replacement level (with immigration making up the rest).
美国和英国则是例外，它们都有大量工作妇女，且生育率接近替代水平（不足部分有移民补充）。