Figure 4.

Correlation between effective reproduction number and test positivity rate in 17 countries. Spearman’s rank correlation coefficients between Rt and rate of test positivity are shown for 17 countries from 1 August 2020 to 17 January 2021. Day-by-day rates of test positivity were shifted ±20 days (by 5 days) for the calculation of correlation coefficient to see the time-lagged preceding and following associations with Rt. Countries were categorized into five groups described in the main text.