Abstract: The future is uncertain, and so are the future populations. This uncertainty is a fundamental aspect of population dynamics. It is affected by various factors such as socio-economic development, technological advances, and even cultural change. Understanding demographic uncertainty is essential in policy-making based on population projection. In recent decades, various methods have been developed to describe the uncertainty, including probabilistic forecast. However, such methods have not got enough attention in China, where the population tends to be highly uncertain due to rapid demographic transition and social transformation. In this paper, we investigate the uncertainty and its policy implications. Specifically, we focus on three major aspects of China's population:the number of births, particularly in the era of universal two-child policy, the number of total population, and the target population of regional planning. Overlooking or underestimating demographic uncertainty can lead to misleading projection results for policy makers and the public. We are in need of developing methods for China's population projections.

Keywords: Demographic Uncertainty, Stochastic Forecasts, Deterministic Projection, Population Planning

摘要： 不确定性是人口动态过程的基本特征，受到社会经济、文化技术等诸多因素的影响，并伴随着人类社会的演化而不断变化。科学处理人口不确定性是进行知情决策的关键。在梳理人口不确定性的来源、形成机制和特点，以及对确定性预测和随机人口预测的优缺点进行总结和评析的基础上，实证剖析了近年来中国出生人口数、总人口规模以及区域人口规划的不确定性，阐释忽视不确定性可能造成的对人口形势的误判，讨论如何正确解读随机人口预测结果和人口不确定性的政策含义。中国亟需深化人口不确定性理论和方法领域的研究，加强随机预测方法的应用与推广，为应对不断增长的人口不确定性和提高人口知情决策的科学性和实用性提供坚实的基础。

关键词: 人口不确定性, 随机人口预测, 确定性预测, 人口规划