Diagram of the Causes of Mortality in the Army in the East

Florence Nightingale’s polar area diagram (often called the “rose diagram” or “coxcomb chart”) was a revolutionary act of data-driven advocacy. Created in 1858, it showed that far more British soldiers died from preventable diseases (blue) than from battle wounds (red) or other causes (black) during the Crimean War.

Nightingale was not the first to use this chart type — André-Michel Guerry had used similar forms earlier — but she was the first to weaponize it politically. She sent the diagrams directly to Queen Victoria and Members of Parliament, leading to sweeping reforms in military hospital sanitation.

The design choice was deliberate: a pie chart would have worked mathematically, but the radial area form was more dramatic and intuitive for her non-technical audience. It proved that choosing the right visualization for your audience is as important as choosing the right one for your data.