How to change the world with data visualisation

8th February, 2022

“She may look at it because it has pictures.” That was Florence Nightingale’s withering comment, as she sent a report about public health reform to Queen Victoria.
Nightingale was not much impressed with the Queen (“The least self-reliant person I have ever known”). But she clearly understood her audience: if you want to get a message across, paint a picture.
Nightingale’s message could hardly have been more important. After famously serving in an Istanbul hospital during the Crimean war, she returned from the place she called “the kingdom of hell” with a reforming mission.
The hospital had indeed been hellish. Men would arrive, bleeding from abdominal wounds, their bodies crawling with vermin; and leave, stitched up in their own blankets to be carried to a mass grave.
In January 1855 alone, the British army in Crimea lost one man in ten to the ravages of diseases such as dysentery and cholera. Nightingale was attempting – at first without success – to prevent a humanitarian catastrophe, as infectious disease tore the British Army to shreds.
But Nightingale found that the death toll in the hospitals was dramatically reduced after improvements to hygiene – whitewashing walls, for example, and pulling a dead horse out of the water supply.
She believed that similar efforts at public hygiene could dramatically improve public health back in Britain. What had worked in Istanbul could work elsewhere. “Nature is the same everywhere, and never permits her laws to be disregarded with impunity,” she noted.
The insight was to drive her campaigning back in the UK. She was one of the only figures to emerge from the disaster of the Crimean War with reputation intact. But despite her celebrity, she had an uphill struggle to convince the medical establishment.
With germ theory in its infancy, Nightingale’s ideas were viewed as radical and, by many doctors, implausible. The chief medical officer, John Simon, opined in 1858 that as a cause of premature death, contagious diseases were “practically speaking, unavoidable”.
Nightingale was not only a nurse and a national icon, but a statistician, the first female fellow of the Royal Statistical Society. She had used her understanding of data to track the link between sanitary improvements and the falling death rate in the Istanbul hospitals.
To turn that understanding into action required statistical persuasion. With geek allies such as William Farr and John Sutherland, Nightingale began to campaign for better public health measures. But the crucial weapon in that campaign was Nightingale’s data visualisation – most famously her “rose diagram”.

The most famous of Florence Nightingale’s “rose diagrams”, “Diagram of the causes of mortality in the army of the east”

This diagram, easily dismissed as mere decoration, was to change the world. As a piece of statistical rhetoric it is breathtaking, telling a compelling story of disaster before the sanitary improvements, and redemption afterwards. Those two pale circles delivered a powerful two-part payload; John Simon and his allies felt the force of both barrels.
But as striking as the diagram itself was Nightingale’s insight into the importance of data visualisation, at a time when British statisticians would invariably rely on tables of data.
On Christmas Day 1857, she sketched out a plan to use data visualization for social change. She declared her plan to have her diagrams glazed, framed, and hung on the wall at the Army Medical Board, Horse Guards, and War Department. “This is what they do not know and did ought to.”
And she planned to distribute her diagrams to exactly the right people.
“None but scientific men even look into the appendices of a Report, and this is for the vulgar public . . . Now, who is the vulgar public who is to have it? … The queen … Prince Albert . . . all the crown heads in Europe, through the ambassadors or ministers of each … all the commanding officers in the army … all the regimental surgeons and medical officers . . . the chief sanitarians in both houses [of Parliament] … all the newspapers, reviews and magazines.”
John Simon and his allies were helpless before this onslaught. Nightingale and her allies – and, particularly, her graphical rhetoric – proved irresistible. Public health practice evolved, new sanitary laws were passed, and John Simon quietly revised his views about the inevitability of death from contagion.
Every modern data visualisation expert has an opinion on Nightingale’s graphs. Some find them breathtaking, others confusing or even misleading. But to my mind, there is something shockingly, brilliantly modern about the battle she decided to fight, and the way she used persuasive data visualisations as her weapon.
More than ever, we need to understand how data visualisation works. We need to understand it as consumers – who may be enlightened or bamboozled, depending on our own “graphicacy” and the choices made by the producers of graphs.
And we need to understand data visualisation as producers. Graphs and diagrams are powerful tools, supercharged by the ready availability of data and versatile software. But like any tool, they can be used skilfully or clumsily. They may be used to build something wonderful, or repurposed as weapons.
For an insight into the power and the sorrows of data visualisation, we could do worse than think of Florence Nightingale’s campaign to change the world with a souped-up pie chart.

To find out more about Florence Nightingale, data visualisation and the uses and misuses of data, please note that the paperback of The Data Detective was published on 1 February in the US and Canada. Title elsewhere: How To Make The World Add Up.

If you would like to hear Helena Bonham Carter in the role of Florence Nightingale (she’s incredible) then check out this episode of Cautionary Tales.

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