But what percentage are pre-symptomatic? If cases are doubling every 5 days, and it takes 5 days for symptoms to show, might that explain result?<p>However the Italian study appears to agree with this preprint about another complete population study: <a href="https://www.medrxiv.org/content/10.1101/2020.03.05.20031773v2.full.pdf" rel="nofollow">https://www.medrxiv.org/content/10.1101/2020.03.05.20031773v...</a><p>That paper shows that the effect is age related: People over ~50 have a ~50% chance of being asymptomatic, under 50 years is ~10% asymptomatic.