Victorian icon Florence Nightingale is best known as the founder of modern nursing. But Nightingale, who would have celebrated her 200th birthday on May 12, was also a statistics and data visualization pioneer who sought to illustrate that simple sanitation techniques, such as handwashing, could stop the spread of infectious diseases (SN: 1/5/20). While that’s a particularly timely message given the ongoing coronavirus pandemic, it wasn’t one widely known, or even believed, in the mid-1800s.

Nightingale’s best-known diagram is a variation of a pie chart known as a rose, or polar area, chart. In that diagram, she showed that poor sanitation, not battle wounds, lay behind most English soldiers’ deaths during the Crimean War in the 1850s and that such deaths were avoidable, says statistics historian Eileen Magnello of University College London. It “provided unequivocal evidential data that preventable contagious diseases could be eliminated.”

To make the graph, Nightingale used data she and medical staff collected while caring for English soldiers in army hospitals and camps. She observed the soldiers’ horrific living conditions — dirty linens, clothes infested with lice and fleas, and rats hiding under the beds. Far more soldiers, she realized, were dying of diseases, such as cholera, typhus and dysentery, than battle wounds.

That graph wasn’t Nightingale’s only attempt at data visualization: She made a series of other charts to help convince the general public, medical staff and lawmakers that sanitation saves lives.

Other “bat’s wing” diagrams were precursors to the rose charts. In one example, Nightingale compares causes of English soldiers’ deaths during the Crimean War from April 1854 to March 1855 by month with deaths from April 1855 to March 1856. These diagrams were meant to show that sanitation efforts implemented in army camps and hospitals during the war dramatically cut soldiers’ deaths. The length of each radial line is proportional to the death rate for that month, with a large spike in deaths in January 1855.

But the text accompanying the diagrams suggested the shaded areas, not the radial lines, correspond to the death rate. Nightingale put an erratum on the figure and stopped using it, showing she arrived at her iconic rose chart through trial and, even, error.

Visualizations became one of Nightingale’s preferred ways of communicating about the need for sanitary reforms to save lives, a sentiment she herself expressed in a letter dated August 1857: “Whenever I am infuriated, I revenge myself with a new diagram.” 

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