Crude COVID-19 case fatality rates (number of known cases divided by number of deaths) by age group. Data  for countries:
<ul><li><div class="legend" style="direction:ltr;line-height:23px;"><div class="legend-content" style="display:inline-block;vertical-align:top;box-sizing:border-box;width:34px;height:23px;overflow:hidden;font-size:15px;border:thin solid #333;background:#d62728;color:#202122;text-align:center;"> </div> China - until 11 February 2020, source: <i>China CDC Weekly</i> <a rel="nofollow" class="external autonumber" href="http://weekly.chinacdc.cn/en/article/id/e53946e2-c6c4-41e9-9a9b-fea8db1a8f51">[1]</a></div></li>
<li><div class="legend" style="direction:ltr;line-height:23px;"><div class="legend-content" style="display:inline-block;vertical-align:top;box-sizing:border-box;width:34px;height:23px;overflow:hidden;font-size:15px;border:thin solid #333;background:#2ca02c;color:#202122;text-align:center;"> </div> South Korea - until 15 April 2020, source: Korea Centers for Disease Control and Prevention <a rel="nofollow" class="external autonumber" href="https://www.cdc.go.kr/board/board.es?mid=a30402000000&amp;bid=0030">[2]</a></div></li>
<li><div class="legend" style="direction:ltr;line-height:23px;"><div class="legend-content" style="display:inline-block;vertical-align:top;box-sizing:border-box;width:34px;height:23px;overflow:hidden;font-size:15px;border:thin solid #333;background:#ff7f0e;color:#202122;text-align:center;"> </div> Spain - until 16 April 2020, source: Ministry of Health <a rel="nofollow" class="external autonumber" href="https://www.mscbs.gob.es/profesionales/saludPublica/ccayes/alertasActual/nCov-China/documentos/Actualizacion_78_COVID-19.pdf">[3]</a></div></li>
<li><div class="legend" style="direction:ltr;line-height:23px;"><div class="legend-content" style="display:inline-block;vertical-align:top;box-sizing:border-box;width:34px;height:23px;overflow:hidden;font-size:15px;border:thin solid #333;background:#1f77b4;color:#202122;text-align:center;"> </div> Italy - until 16 April 2020, source: Italian National Institute of Health <a rel="nofollow" class="external autonumber" href="https://www.epicentro.iss.it/coronavirus/bollettino/Bollettino-sorveglianza-integrata-COVID-19_16-aprile-2020.pdf">[4]</a></div></li></ul>
These reports contain number of cases and deaths that were laboratory-confirmed at the date of the report. As not every case is detected (probably most are undetected, and this ratio is different for each country), testing and gathering statistics takes time, and some who are now confirmed will die in the future, this method of CFR calculation is a rather inaccurate. But as it is just the division of two numbers, it can be done quickly with publicly accessible data.
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<span class="int-own-work" lang="en">Own work</span>