This is the diagram that Florence Nightingale (the nurse during the war) created to show the fatalities in hospitals to the Government. She wanted a visual representation because this would have the most impact.
This is effective because it shows the sheer amount of fatalities due to infections with the use of area and colour. The circle is divided from the centre into 12 segments with different radiuses to represent different amounts of causes of death.
It shows that even in the old periods that people used circles which are trending today in the design industry. In addition is relates the use of time with circles. A circle is a good shape to represent the year because each month has similar amount of days therefore the segment point is the same but the radius is not the same because it is a variable factor.