[criticaltinker]

That CDC estimate is based on a simple probabilistic multiplier model from data up to Nov 2020 [0].

More recent meta-analyses [1] and large population-based serological studies [2] suggest a lower bound for the asymptomatic proportion to be at least ~33%. For young adults the upper bound for asymptomatic rate is likely between 65%-90% (95% CI) [2]. Considering other recent evidence that cases may be massively underreported [3], the true asymptomatic proportion could be even higher than what has been suggested.

[0] Estimated Incidence of Coronavirus Disease 2019 (COVID-19) Illness and Hospitalization—United States, February–September 2020 https://academic.oup.com/cid/article/72/12/e1010/6000389

[1] The Proportion of SARS-CoV-2 Infections That Are Asymptomatic https://www.acpjournals.org/doi/full/10.7326/M20-6976

[2] Estimating the asymptomatic proportion of SARS-CoV-2 infection in the general population: Analysis of nationwide serosurvey data in the Netherlands https://link.springer.com/article/10.1007/s10654-021-00768-y

[3] Evaluating the massive underreporting and undertesting of COVID-19 cases in multiple global epicenters https://www.sciencedirect.com/science/article/pii/S253104372...