In Spring 2003 I published A Global Model of Population-Resource Interaction in NRM (Published on line by Wiley in June, 2008). After 20 years it may be time to see how prediction compares with observation.

Today (July 1, 2023) the UN World Population Dashboard puts world population at 8.045 billion. The 2003 model predicted 7.8 billion. The UN measurement of world population has consistently outpaced model predictions up to the present date and, if anything, the gap is getting wider—in the neighborhood of 0.2 or 0.3 billion. The population data below are from World Population Prospects, 2022.

(Year, UN Measure of Global Population, Model Prediction, Difference)

(2000, 6.1, 6.0, 0.1); (2003, 6.4, 6.3, 0.1); (2005, 6.6, 6.5, 0.1); (2010, 7.0, 6.9, 0.1), (2013, 7.3, 7.1, 0.2); (2015, 7.4, 7.3, 0.1); (2020, 7.9, 7.6, 0.3); (2023, 8.0, 7.8, 0.2).

Today the UN predicts peak population at nearly 10.4 billion in the mid 2080s.

The best fit of the model predicts a peak of 8.8 billion in the mid 2050s. A thousand runs of the model with parameters varying indicated a statistically closer prediction might be a peak somewhat higher and later, but unlikely to be as high and as late as that of the UN.

2003年春，我在NRM上发表了《A Global Model of Population-Resource Interaction》（Wiley于2008年6月在线发布）。20 年后，也许是时候看看预测与观察有何不同。

今天（2023 年 7 月 1 日）联合国世界人口仪表板显示世界人口为 80.45 亿。2003 年的模型预测为 78 亿。迄今为止，联合国对世界人口的测量一直超过模型预测，而且差距正在扩大——接近 0.2 或 3 亿。以下人口数据来自《2022 年世界人口展望》。

（年份，联合国全球人口衡量标准，模型预测，差异）

(2000, 6.1, 6.0, 0.1); (2003, 6.4, 6.3, 0.1); (2005, 6.6, 6.5, 0.1); (2010, 7.0, 6.9, 0.1), (2013, 7.3, 7.1, 0.2); (2015, 7.4, 7.3, 0.1); (2020, 7.9, 7.6, 0.3); （2023、8.0、7.8、0.2）。

如今，联合国预测 2080 年代中期人口将达到峰值，接近 104 亿。

该模型的最佳拟合预测在 2050 年代中期将达到 88 亿的峰值。参数变化的模型的一千次运行表明，统计上更接近的预测可能是一个更高和更晚的峰值，但不太可能像联合国那样高和晚。