Although there are many factors that will influence how deadly COVID-19 is, we can already start to sketch out some predictions on the ultimate Infection Fatality Rate (IFR) for each country. We'll start by considering only age - this appears to be the biggest determinant for how deadly COVID-19 is (Figure 1).
Figure 1: Infection Fatality Rates by age category. Someone who is 80+ is 10 times as likely to die as someone in their sixties, and 5,000 times more likely to die than a 15 year old.
This has dramatic implications for the predicted IFR for different countries. On the two extremes would be countries like Japan (oldest) and Nigeria (among youngest).
Figure 2: The difference in percentage of the population is dramatic. For example, people over 80 represent almost 10% for Japan and only 0.5% for Nigeria.
The difference in age demographics translates into a dramatic predicted IFR for the two countries (1.25% for Japan versus 0.165% for Nigeria). There are other determinants for IFR (cardiovascular health, obesity, medical facilities, etc.) but age is undoubtedly the dominant factor. Based on age alone, we show predicted COVID IFR for 10 countries below:
Figure 3: Expected IFR for 10 selected countries.