University of Michigan - Ann Arbor

- It is estimated that in the absence of policies, early infection rates of COVID-19 grow 43% per day on average across China, South Korea, Italy, Iran, France, and the United States. This implies a doubling time of approximately 2 days.
- Country specific estimates range from 34% per day in the US to 68% per day in Iran. 
- However, it cannot be determined whether the high estimate for Iran results from true epidemiological differences, data-quality issues, or the concurrence of the initial outbreak with a major religious holiday and pilgrimage. 
- Excluding Iran, the average growth rate is 38% per day in across the five other countries. 
- Growth rates in all five other countries are independently estimated to be very near the average growth rate. These estimated values differ from observed average growth rates because the latter are confounded by the effects of policies. 
- The growth rates are not driven by the expansion of testing or increasing rates of case detection. 

Estimates for Growth Rates

Hsiang, S., Allen, D., Annan-Phan, S. et al. The effect of large-scale anti-contagion policies on the COVID-19 pandemic. Nature 584, 262–267 (2020). https://doi.org/10.1038/s41586-020-2404-8

The effect of large-scale anti-contagion policies on the COVID-19 pandemic

Figure of Empirical estimates of unmitigated COVID-19 infection growth rates and the effect of anti-contagion policies.

- Combined effect of policies within each country reduces the growth rate of infections by a substantial and statistically significant amount.
- In general, the estimated total effects of policy packages are large enough that they can in principle offset a large fraction of, or even eliminate, the baseline growth rate of infections—although in several countries, many localities have not deployed the full set of policies.
- The deployment of anti-contagion policies in all six countries significantly slowed the pandemic. The empirical estimates with the data on the timing of the 1,700 policy deployments was used to estimate the total effect of all policies across the dates in our sample. 

Learn Before

Related