On January 30, 2020, the World Health Organization (WHO) declared SARS-CoV-2 a global pandemic, based on a high infection rate and a high case fatality rate (CFR). The combination of these two points led WHO to forecast a high expected mortality rate of approximately 2% of the population. The phenomenon of Simpson’s paradox teaches us that we should be careful when we combine two variables together. Indeed, despite the high mortality rate in several places, this forecast seems to have collapsed. We believe one of the reasons for the erroneous forecasts is that combining the above points ignored a confounding variable – many of the virus carriers are asymptomatic and therefore not diagnosed.

2020 年 1 月 30 日，世界卫生组织 (WHO) 基于高感染率和高病死率 (CFR)，宣布 SARS-CoV-2 为全球大流行。综合这两点，世界卫生组织预测人口死亡率很高，约为 2%。辛普森悖论的现象告诉我们，将两个变量组合在一起时要小心。事实上，尽管一些地方的死亡率很高，但这一预测似乎已经崩溃。我们认为，预测错误的原因之一是综合上述几点忽略了一个混杂变量——许多病毒携带者没有症状，因此未被诊断出来。