普遍认为在发达国家人口增长的主要原因与其说是出生率的上升还不如说是由于医疗保健的改善使死亡率下降了
It is generally believed that the main reason for population growth in developed countries is not so much the increase in the birth rate as the improvement in healthcare, which has led to a decline in the death rate
以上为机器翻译结果，长、整句建议使用 人工翻译 。