NBER Working Papers · 2026 · Seth G. Benzell、Laurence J. Kotlikoff、Victor Yifan Ye
中文摘要
本研究采用一个多区域、动态生命周期一般均衡模型，评估本世纪人口结构对全球发展的影响。模型涵盖17个区域、150多个国家，其人口占世界总人口的99%。产出由三个技能组别的劳动力和可跨国流动的资本共同创造，各国每年决定是否采用其前沿自动化技术。模型纳入了区域特定的财政政策、全要素生产率增长和个体特有的死亡风险。行为主体的寿命为100年，依次经历儿童期、工作期和退休期。工作与储蓄决策由CES偏好决定。寿命具有不确定性，但除国家养老金外不存在年金。因此，遗赠尽管数额可观，却并非出于主观意愿。模型中的生育率、死亡率和净移民率均因区域和年龄而异，并与联合国的预测完全一致。为说明人口结构影响全球转型的强大作用，我们分别采用联合国2017年和2024年差异显著的人口预测进行模型模拟。2024年的预测对中国的生育前景尤为悲观。两组预测均显示全球人口将大幅老龄化，并将出现严重的全球资本过剩，使长期实际资本回报率降至很低水平。最新预测意味着2100年全球GDP将降低10%，而为老年福利筹资所需的工资税税率将高得多。最重要的是，该预测意味着经济霸权的演变轨迹将发生重大变化：中国在2100年全球GDP中的占比将从25.6%降至14.9%，美国的占比则从11.2%升至14.4%。我们的结果较为敏感。如果美国完全取消未来所有移民，其2100年占全球GDP的14.4%将降至9.2%。如果全球生育率遵循联合国的低方案，2100年世界产出将降低三分之一，而非十分之一。全球产出的水平及其分布也对人工智能拓展前沿技术的速度高度敏感。加速型自动化/人工智能——截至2050年资本份额的增长速度为近期增速的4倍——或变革型自动化/人工智能——资本份额的增长速度为近期增速的10倍——将强化人口结构力量，确保美国长期保持经济霸权。事实上，变革型人工智能与2024年人口结构相结合，意味着美国和中国在2100年全球GDP中的占比将分别为25.3%和16.9%。尽管中国在技术上大幅追赶，但根据我们的校准结果，美国在整个本世纪仍将保持对中国的技术优势。
Abstract
This study deploys a multi-region, dynamic life-cycle, general equilibrium model to assess demography’s impact, through the course of this century, on global development. Our model’s 17 regions encompass more than 150 countries comprising 99% of the world’s population. Output is produced with three labor skill groups and internationally-mobile capital, with each country deciding annually whether to adopt its frontier automation technology. Our model features region-specific fiscal policy, TFP growth, and idiosyncratic mortality. Agents live for 100 years, first as children, then as workers, and then as retirees. Work and saving decisions are governed by CES preferences. Lifespan is uncertain, but there are no annuities apart from state pensions. Hence, bequests, while significant, are unintended. Our fertility, mortality, and net immigration rates are region- and age-specific and align fully with the UN’s projections. To illustrate demographics’ power to impact the global transition, we simulate our model under the UN’s markedly different demographic projections for 2017 and 2024. The 2024 forecast is particularly pessimistic about China’s fertility prospects. Both projections produce very substantial global aging, a major global capital glut producing very low long-run real capital returns. The latest forecast entails 10% lower global GDP in 2100 and far higher payroll tax rates to fund old-age benefits. Most important, it entails a major change in the course of economic hegemony with China’s 2100 global GDP share falling from 25.6% to 14.9% and the US share rising from 11.2% to 14.4%. Our results are sensitive. Should the US eliminate all future immigration, its 14.4% global 2100 GDP share would drop to 9.2%. And were global fertility to follow the UN’s low variant, 2100 world output would be one third, not one tenth lower. The level and division of global output is also highly sensitive to the speed at which AI expands frontier technologies. Accelerated AU/AI – 4x faster-than-recent growth in capital’s share through 2050 – or Transformative AU/AI – 10x faster capital-share growth – reinforce demographic forces, ensuring long-run US economic hegemony. Indeed, Transformative AI combined with 2024 demographics implies US and Chinese 2100 global GDP shares of 25.3% and 16.9%, respectively. And not withstanding its considerable technological catch up, the US retains, based on our calibration, a technological edge over China throughout the century.