以宁波市为例，基于宁波市“六普”与“五普”数据，首先利用年龄别死亡率对同批次队列人口进行年龄移算，即人口留存分析，对比2010年的实际人口数和无迁移模式下的封闭人口数之差，进一步测算两次普查期间分性别、年龄别人口的净迁移量和净迁移率。然后，将迁移率与出生率和死亡率整合，构建多要素随机人口预测模型，预测宁波市未来人口变化趋势，并评估迁移、死亡、出生三要素对人口变动的弹性影响效果。结果表明：人口净迁入对宁波市人口总量变化影响最大，而低死亡率和低出生率是未来50年加剧宁波市人口老龄化的主要原因。未来50年内，劳动力人口净迁入对降低宁波市人口老年负担系数的作用有限。鼓励夫妇生育二孩，优化人才引进与落户机制，尽快建立起应对高龄社会的公共服务体系尤其是长期照护体系，应是宁波市人口政策改革的当务之急。%The traditional methods of population projection are often without the parameters of migration, or only contain the total rate, let along the age⁃specific migration rate. This paper provided a stochastic method with the factor of migration for the regional district. Firstly we did a reverse comparison based on the 6 th and 5 th national census and calculated the age⁃specific migration rate, by gender, between two census in Ningbo. Based on the stochastic projection model and under five scenario analyses, this paper forecasted the population trend and ageing process. Meanwhile, we evaluated the effect of different parameters (migration, birth, death). Prediction results show that migration is the key impact factor to the population size and the low⁃level of mortality and fertility are the main reason of ageing. This method can be widely applied to various regions and help the local government to take effective demographic policies. The total population tends to get more than 9 million, although the migration level has a decrease trend. The young labor migration works will have a limited effectiveness to pull down the upsurge of the old dependency ratio in Ningbo city. The government should take measures to boost the birthrate, improve the hukou policy to encourage talent migrants settle down and should establish a completed social security system before the coming of elderly society.
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