The chart operates on absolute numbers and starts from a 100th case, which for smaller countries means a higher percentage of population already infected.

Sources:

• https://www.ft.com/content/a26fbf7e-48f8-11ea-aeb3-955839e06441
• https://www.heritage.org/index/ranking
• https://en.wikipedia.org/wiki/Hong_Kong
• https://en.wikipedia.org/wiki/Singapore