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。
2
Europeans, with their confidence returning, went forth, multiplied and buried many a hatchet. Rising fertility and Europe's integration became the main motors of the continent's economic boom.