Distribution of the main covariates and control variables for the COVID waves (March and October 2020); separated and pooled samples.

Distribution of the main covariates and control variables for the COVID waves (March and October 2020); separated and pooled samples.2020年3月与10月两波新冠疫情浪潮下，主要协变量（covariates）与控制变量（control variables）的分布情况；分析涵盖拆分样本与合并样本两种样本设置。