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Here is a distribution of recorded Covid-19 cases in Iceland (which tests broadly, even people with no symptoms) and the Netherlands (which tests narrowly, only those with severe symptoms)
Sources:
NL: https://www.rivm.nl/sites/default/files/2020-03/Epidemiologische%20situatie%20COVID-19%2027%20maart%202020.pdf
IS: https://www.covid.is/data
NL: https://www.rivm.nl/sites/default/files/2020-03/Epidemiologische%20situatie%20COVID-19%2027%20maart%202020.pdf
IS: https://www.covid.is/data
On the Icelandic testing strategy: https://www.buzzfeed.com/albertonardelli/coronavirus-testing-iceland
On the Dutch lack of testing: https://www.nrc.nl/nieuws/2020/03/23/we-testen-veel-maar-niet-te-veel-a3994668
The vertical axis are percentages of course.
NB: Germany is planning a large 100'000 randomised blood survey to assess who has it, who is immunised, etc. https://www.spiegel.de/wissenschaft/medizin/coronavirus-grosse-antikoerper-studie-soll-immunitaet-der-deutschen-feststellen-a-c8c64a33-5c0f-4630-bd73-48c17c1bad23
