Florence Nightingale: Data Viz Pioneer

Roman Mars:
This is 99% Invisible. I’m Roman Mars.

Roman Mars:
It’s pretty easy to lie with statistics, but it’s really easy to lie with statistics when there is a pretty drawing attached. What follows is a story of data visualization and coercion, and it centers on a person not particularly well-known for either one of these things — the founder of modern nursing, Florence Nightingale. And the perfect person to tell this story is Tim Harford, the undercover economist, the author of “The Data Detective” and the host of the podcast “Cautionary Tales,” which has just started its new season. I could not be more excited. I love the show. I’m so happy it’s back. And this episode that we have the honor of premiering is tailor for the 99pi crowd. So without further ado, here’s Tim Hartford.

Tim Harford:
The grand barracks at Scutari in Istanbul was said to be the largest in the world when they were completed in the 1820s. By the 1850s, a grim war would turn them into the world’s largest hospital.

Florence Nightingale (voiced by Helena Bonham Carter):
To inexperienced eyes, the Scutari buildings were magnificent. To us, in their first stage, they were truly whited sepulchers. Pest houses.

Tim Harford:
Those are the words of a British nurse named Florence Nightingale. She sailed out to Istanbul during the Crimean War. A pointless conflict between Russia and an alliance, including the British. Nightingale arrived late in 1854 with a small team of nurses. Her task was to assist in the care of wounded British soldiers coming back from the battlefront to the hastily converted barracks hospital at Scutari. What did they discover waiting for them?

Florence Nightingale (voiced by Helena Bonham Carter):
Oh, you gentlemen of England can have little idea from reading the newspapers of the horror and misery of operating upon these dying and exhausted men. That this is the kingdom of hell, no one can doubt.

Tim Harford:
Within days of her arrival, with fewer than 40 nurses, hundreds of casualties started arriving every day from the fighting in the Crimean peninsula. These men were bleeding from abdominal wounds, their faces black with gunpowder and mud, their bodies crawling with vermin. After each man died, he’d be stitched up in his own blanket and carried to a mass grave, making space for the next to take his bed. As for the hospital itself, Nightingale was appalled by the conditions and the shambolic organization. The heating system didn’t work and there was no clean water. The army supply chain sent the wrong equipment to the wrong place at the wrong time as a matter of routine. And they also seemed to delight in refusing to deal with Nightingale, a woman in a man’s world.

Florence Nightingale (voiced by Helena Bonham Carter):
No mops, no plates, no wooden trays, no slippers, no shoe brushes, no blacking, no knives and forks, no spoons, no scissors for the cutting of men’s hair, which is literally alive. No basins, no toweling, no chloride of lime.

Tim Harford:
What unfolded that winter was a catastrophe. In January 1855, the British Army in Crimea lost one man in ten to the ravages of diseases, such as dysentery and cholera. Many of them died at the hospitals in Scutari. Infectious disease tore the British Army to shreds. Back in the UK, the reputation of the generals and politicians was also in tatters. One figure alone emerged with reputation intact — Florence Nightingale. The leader of the nurses in Istanbul was celebrated as the lady with the lamp, a near-religious icon of gentleness and dedication, and the most famous woman in the British empire, except Queen Victoria herself.

Queen Victoria (voiceover):
There is not one of England’s proudest and purest daughters who at this moment stands on so high a pinnacle, this Florence Nightingale.

Tim Harford:
The soldiers loved her, too.

Soldier (voiceover):
If there is any angels on earth, she is one. What glory to see her delicate form gliding about amongst hundreds of great rough soldiers and to see the looks of love and gratitude that they cast on her beloved face. It would be a brave man that dare insult her. I would not give a penny for his chance.

Tim Harford:
In May 1855, with conditions at her hospitals improving, Florence Nightingale sailed to the front in Crimea, where she was moved both by the spectacle and by the devotion of the men.

Voiceover:
The men of the 39th regiment turned out and gave Florence Nightingale three times three, as I rode away, there was nothing empty in that chair.

Tim Harford:
Florence Nightingale was becoming a saint. But the battle with a disease that had shaped her reputation was about to take a sudden turn. On the 13th of May, a few days after arriving in Crimea and just a day after her 35th birthday, she collapsed. The rumors quickly spread around the British Army, Florence Nightingale was dying.

Tim Harford:
I’m Tim Hartford and you’re listening to “Cautionary Tales.”

[MUSIC]:

Tim Harford:
Even today, it is as a nurse that Florence Nightingale is revered in Britain. 25 years ago, my mother took her last breath in a Nightingale hospice. Nightingale’s face adorned British banknotes and the front cover of magazines during the COVID-19 pandemic.

Voiceover:
All hail the hand-washing queen.

Tim Harford:
And we even named our emergency COVID hospitals the “Nightingale Hospitals.” Nightingale is the ultimate nursing icon. It’s as though she had died the day she collapsed in Crimea in May, 1855 at the age of 35. Her mission as a nurse had been accomplished. Her march to heaven was assured and there was nothing more to be said, which is strange because despite the trauma and the sickness staying with her, Nightingale lived until she was 90-years-old. And she didn’t bask in her celebrity, nor retire to her country home. She had a much bigger battle to fight.

Tim Harford:
One woman and a handpicked team of geeks versus the entire military and medical establishment of the country with hundreds of thousands of lives at stake. That huge fight is what this cautionary tale is about. That, and the strangely modern weapon she used, because Florence Nightingale was not only a nurse, she was also… and I mean this as a most sincere compliment, a total nerd. She became a statistician, the first female fellow of the Royal Statistical Society and an honorary member of the American Statistical Association. She was a master of data visualization. If you wanted to be dismissive, and some people do, you’d say she was very good at drawing pretty diagrams, but those pretty diagrams changed the world. This is the story of how to fight for a public health revolution armed with a souped-up pie chart.

Tim Harford:
I don’t need to tell you how ubiquitous data visualization is. Everywhere we look, whether we check social media, turn on rolling news or flip through a newspaper, we see graphs and charts — flashy pictures of data, designed to persuade us of something. They’re not just decorations. These graphs push and pull us into taking high-stakes decisions. COVID-19 reminded us of just how high the stakes can be. People have lived or died because of the decisions they’ve made after looking at a chart on Facebook. That’s why I wanted to understand what Florence Nightingale did with graphs and how she did it. But the deeper I went into the Florence Nightingale archives, the stranger the story became. And it raises a question — if graphs are so powerful, shouldn’t we worry about how that power is used?

Tim Harford:
From the hospital in Scutari, Florence Nightingale had tirelessly lobbied for support and assistance, expertly dealing with the press and her political contacts to get what she needed. And in March 1855, came a turning point. A sanitary commission arrived from Britain with the task of cleaning up the hospitals in Scutari. There was a lot of cleaning to do. Over the following weeks, they discovered that the drains leading away from the Barrack hospital were blocked, effectively meaning that the hospital sat on a cesspool. The main water pipe supplying part of the hospital was blocked by a decomposing horse. Two dozen more animal carcasses were found on the hospital site. Prefabricated privy’s had been built in the central courtyard, but excrement was leaking out of the trench beneath them and into an adjacent water tank. By late March, the army was carrying out the commission’s recommendations, clearing and flushing the sewers, cutting air vents in the ceilings, removing rotten wood floors, and whitewashing everything.

Florence Nightingale (voiced by Helena Bonham Carter):
The sanitary commission is really doing something and has set to work burying dead dogs and whitewashing walls, two prolific causes of fever.

Tim Harford:
The death toll was far lower after the commission had done its work than before. It was a perfect example of what could be achieved to save lives with simple cleanliness and keeping sewage away from the water supply. And Nightingale did not forget the lesson. When Florence Nightingale returned from the war, Queen Victoria summoned her for a Royal audience.

Queen Victoria (voiceover):
Ah, Ms. Nightingale.

Florence Nightingale (voiced by Helena Bonham Carter):
Your Majesty.

Queen Victoria (voiceover):
We have heard so much about you.

Tim Harford:
Nightingale didn’t think much of Victoria.

Florence Nightingale (voiced by Helena Bonham Carter):
She is the least self-reliant person I’ve ever known.

Tim Harford:
But the queen could be useful to her. Florence Nightingale had returned from the kingdom of hell with a mission. She wanted to make sure the awful toll of disease in Scutari never happened again in any British hospital, anywhere in the world. So Nightingale persuaded Victoria to support a Royal Commission investigating the health of the army. As a woman, Nightingale was unable to sit on the commission herself, but she assembled her geek allies and worked behind the scenes to figure out the problem. She turned down Queen Victoria’s offer of a suite at Kensington Palace. There would be far too many visitors. Instead, she took rooms at a low-rent London hotel.

Tim Harford:
So what had been the underlying cause of the death toll in the Scutari hospitals? To modernize, the answer is obvious. Disease spreads thanks to poor hygiene, poor ventilation and contaminated water. The hospitals in Scutari suffered from all three. It was not so obvious to Nightingale. Germ theory didn’t exist in the 1850s.

Tim Harford:
Although the science was mysterious, Nightingale was one of a group of Victorian thinkers who were convinced that one way or another, good sanitation should help. With her ally, the great statistician, William Farr, she assembled and examined the data. Farr and Nightingale became convinced that wherever they looked, premature death went hand in hand with open sewers, bad ventilation and unclean conditions. It wasn’t just about the Crimean War. It was an ongoing public health disaster in barracks, civilian hospitals, and beyond. The pair began to campaign for better public health measures. And here the epic battle was joined. They faced powerful opposition. The government didn’t want an embarrassing report about the Crimean War, already regarded as a fiasco. The queen of course, was an instinctive conservative, whose idea of reform was to replace one over-promoted bureaucrat with another, and neither the army nor the medical profession cared to take instructions from a woman, not even the angel of Scutari, Florence Nightingale.

Tim Harford:
In any case, they believed she was surely wrong. A couple of years after the end of the Crimean War, in 1858, the chief medical officer, John Simon acknowledged that contagious diseases such as cholera and dysentery were-

John Simon voiced by actor:
A cause of premature death in every civilized country.

Tim Harford:
But, that they were-

John Simon voiced by actor:
Practically speaking, unavoidable.

Tim Harford:
“These diseases just happened,” said John Simon, and “Yes, they killed people, deal with it. And don’t take any lessons from Florence Nightingale.” Nightingale was outraged at the complacency. The deaths from disease in British Army barracks were criminally high. It was just as bad, she said-

Florence Nightingale (voiced by Helena Bonham Carter):
As it would be to take 1,100 men out upon Salisbury Plain and shoot them.

Tim Harford:
The same for civilian hospitals, private homes, slums. All over the country, men, women and children were dying. And self-satisfied men like John Simon insisted that these deaths were-

John Simon voiced by actor:
Practically speaking, unavoidable.

Tim Harford:
The chief medical officer, the generals and the entire British establishment stood against her. Her geek sidekick, statistician William Farr, warned her to be careful.

William Farr voiced by actor:
Well, if you do it, you will make yourself enemies.

Florence Nightingale (voiced by Helena Bonham Carter):
After what I’ve seen, I can fire my own guns.

Tim Harford:
And the 19th century heroine had a 21st century weapon. It was a diagram. It’s not an accident that these days we’re surrounded by graphs and charts. They’re the sweet spots between solid statistical evidence on one hand and shareable gifts and filtered photos on the other. Hard data plus striking images, scientific evidence backs up what any news editor or social media consultant will tell you. Graphs attract attention. And they persuade people. Researchers at Tufts Visual Analytics Lab found that people formed an impression of a graphic within 500 milliseconds, just half a second. That’s far too brief to understand what the graph is about, but it’s not too brief to think, “What a mess,” or, “Ooh, shiny.” We respond to images without conscious thought.

Tim Harford:
Another team of researchers, data scientists at New York University, showed people evidence about practical policy questions. For instance, does a high corporate income tax drive jobs overseas? Or does prison work as a deterrent? Sometimes the relevant data was in the form of a table and sometimes in the form of a chart. Unless people already had a strong position on the subject, the charts were much more persuasive than the tables. If you saw a chart, you were much more likely to change your view. That seems obvious today. It wasn’t obvious in the 1850s. Statisticians were much more likely to present their data in the form of a table even if the table sprawled across page after page. Beautiful design was thought to be superfluous. Florence Nightingale, not for the first time in her life, begged to differ. She would create a graph so compelling that the British establishment would have to bow in acquiescence. The graph in question is titled-

Florence Nightingale (voiced by Helena Bonham Carter):
Diagram of the Cause of Mortality in the Army in the East.

Tim Harford:
It was published in 1859. The year after Dr. John Simon declared that death from infectious disease was “practically speaking, unavoidable.” Now, I’m going to try my best to describe this image. I’ve seen an original printing up close in the library of the Royal Statistical Society in London. It’s amazing. But you can find copies online.

Tim Harford:
The first thing you would see, say if you were shown the graph for 500 milliseconds, is that it consists of two pale blue spirals, one larger than the other. Look more closely, and you see that each spiral is built of 12 equally angled wedges. Like the hours of the clock. Some of the wedges are small, clinging near the center. Others sprawl out hugely, which is what gives the diagram this sense of spiraling in or out. The rose diagram is a beautiful image, but describes some horrifying numbers. Each of the wedges represents the deaths in a particular month. And the two circles describe the loss of life over two years, from April, 1854 to March, 1856.

Tim Harford:
The first circle spirals out like a snail. October is not too grave. November, when Nightingale arrived at the hospital in Scutari, is worse. December is worse still. January and February are awful. Swollen wedges of blue so large that they threaten to bleed off the edge of the page itself. In the center of the diagram are tiny black and red wedges. They indicate a handful of deaths from miscellaneous causes and from wounds. The huge blue wedges show the overwhelming death toll from infectious diseases.

Tim Harford:
“No one ever made a decision because of a number. They needed a story,” so said Daniel Kahneman and Amos Tversky, the two psychologists whose collaboration would win Kahneman a Nobel prize after Tversky’s death. And Florence Nightingale’s diagram, more than anything, is a story. The first half of that story is a catastrophe, but the second circle continues the narrative in April, 1855, just after the sanitary commission arrived in Scutari. The change is dramatic. The circle is much smaller. And while the first circle spiraled outward in an ever worsening death count, the second circle shrinks inward as the casualties dwindle. It’s a tale with two halves. After the catastrophe, comes the redemption. In between the two of them, flushing out the sewers, casting away the dead horse, disinfecting the hospital buildings.

Tim Harford:
In 1858, John Simon, the chief medical officer, had declared that death from infectious disease was practically unavoidable. In 1859, Florence Nightingale’s graph said that’s a lie. Not only a deaths avoidable, but with simple, practical measures, the army had avoided them. Those two pale blue circles delivered a powerful two-part payload. John Simon and his allies felt the force of both barrels. As Nightingale explained to an old friend and influential politician-

Florence Nightingale (voiced by Helena Bonham Carter):
Whenever I am infuriated, I revenge myself with a new diagram.

Tim Harford:
The graphs and the rose diagram in particular, were part of a deliberate strategy. In another letter to the same friend, written 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 and War Department.

Florence Nightingale (voiced by Helena Bonham Carter):
This is what they do not know and they’d aught to.

Tim Harford:
She added-

Florence Nightingale (voiced by Helena Bonham Carter):
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, with 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.

Tim Harford:
Nightingale’s visual story was impossible to ignore. Opinion started to shift. Parliament passed new laws. Doctors adopted new practices. Nightingale understood earlier than most that a chart has a special power. But I can’t just end this cautionary tale there, on a happy note, because perhaps charts have a little too much power.

Tim Harford:
Our visual sense is potent. So potent that we even use the phrase, “I see,” as a direct substitute for, “I understand.” Seeing can be believing, but seeing can also mean fooling yourself. Edward Tufty, perhaps the most influential graphical guru alive, understands the power of visual explanation as well as anyone. His books include “Envisioning Information” and “Beautiful Evidence,” but we can envision misinformation too, and it can be just as beautiful. And we can now share it with a click.

Tim Harford:
In mid-March, 2020, as we were just beginning to grasp the enormity of the unfolding pandemic, Eric Feigl-Ding, an epidemiologist with a large following and a quick fire style, fired off a graph from the Centers for Disease Control, with a warning-

Voiceover:
News flash for young people. You are not invincible. You’re just as likely to be hospitalized as older generations, even CDC says so.

Tim Harford:
But the CDC’s graph didn’t show that at all. It showed that vastly more over 45s than under 45s were in hospital. But it was easy to misunderstand the graph if you didn’t look closely at the tiny, tiny labels on the axis. And who looks at the tiny, tiny labels, eh? And so an epidemiologist who should have known better, but was just a little too eager to tweet, unwittingly spread misinformation to his 300,000 followers.

Tim Harford:
It gets worse. A few days later, the right-wing pundit, Anne Coulter, tweeted a pair of graphs and the comment-

Voiceover:
For people under 60, Coronavirus is less dangerous than the seasonal flu.

Tim Harford:
But the graphs showed the precise opposite of Coulter’s claim. COVID-19 was about eight times as deadly as flu for people in their 50s and five times as deadly for people in their 30s and 40s. It’s like tweeting a picture of a cow next to a cat with the title-

Voiceover:
Cows are smaller than cats.

Tim Harford:
Absurd. Except Coulter’s up is down message was retweeted more than 11,000 times. Within a few hours of each other, two Twitter influencers, one overplaying the risk of COVID and the other underplaying it, were tweeting graphs that they hadn’t understood. It didn’t seem to stop those tweets going viral. All too many people seem to think any claim with a graph attached, must be true. People make life-changing decisions because of graphical misinformation like this. Quitting a job in fear, but in fact, the risk is low. Or recklessly exposing others to deadly risk because they’ve been told the virus is fake news.

Tim Harford:
It turns out that data visualization is a dual use technology. It can be a tool or a weapon. Florence Nightingale was perhaps the first person in history to grasp that a well-designed graph, based on solid data can be remarkably persuasive. Experience has taught us the unfortunate lesson that a badly designed graph or a graph based on flimsy data… well, they can be remarkably persuasive too.

Roman Mars:
More of Tim Harford’s “Cautionary Tales” on 99% Invisible after this.

[BREAK]

Tim Harford:
There is a strange twist in this story. Because while Florence Nightingale is revered by many graphic designers, many others despise her Rose Diagram. Edward Tufte, the influential author of “Beautiful Evidence,” criticized the graph on his website.

Voiceover:
The inherent problem is the difficulty of making good comparisons across the wedges. In general, for such small data sets, tables will outperform graphics.

Tim Harford:
The diagram is unclear, and since there aren’t that many numbers to portray, Nightingale should simply have used a table. Nightingale’s statistical contemporaries would have agreed, but I’ve seen the data in Nightingale’s graph presented as a table, and the first thing that sprang to mind was Nightingale’s own comment to her friend, in that Christmas day letter of 1857:

Florence Nightingale (voiced by Helena Bonham Carter):
In this form, printed tables and all in double columns? I do not think anyone will read it.

Tim Harford:
Remember to whom she sent this earth-shaking diagram?

Voiceover:
The Queen, Prince Albert, all the crowned heads in Europe, all the newspapers, reviews, and magazines.

Tim Harford:
Tables can be clearer, but tables don’t grab your attention in 500 milliseconds. And kings and queens and ministers and newspaper editors are busy, as Nightingale rather acidly noted when she sent her report to Queen Victoria.

Florence Nightingale (voiced by Helena Bonham Carter):
She may look at it, because it has pictures.

Tim Harford:
Fine. The message demands a graph, but surely there’s a better, clearer graph conveying the same message. Certainly, that’s what Edward Tufte’s followers believe, in the comments on his website.

Voiceover:
Is it wrong that I’m enraged by a graphic? Good design is not drawing pretty pictures and shoehorning the facts in later.

Voiceover:
These Nightingale roses are just a type of pie chart and contain all the disadvantages of pie charts.

Tim Harford:
Wow. That’s quite a burn.

Voiceover:
The charts are difficult to read. I would have thought that a stacked bar chart on a timescale would have been a better choice.

Tim Harford:
Good idea, let’s try a bar chart. And here’s where the plot thickens. Because when I first saw the data presented as a bar chart, my jaw dropped. It is absolutely clear and easy to read. And that’s the problem. When you see the data presented in a clear modern format, you start to realize something. Maybe Florence Nightingale wasn’t quite as saintly as everyone thought. Florence Nightingale’s diagram divides the data into two halves. That’s not an accident.

Florence Nightingale (voiced by Helena Bonham Carter):
The color diagram number one shows the sanitary stage of the army before the arrival of the sanitary commission. The color diagram number two shows what it became after that event.

Tim Harford:
Catastrophe before, recovery after. And as I’ve mentioned, Nightingale was aiming, not at a post-mortem of the Crimean war, but at the far bigger goal of public health reform.

Florence Nightingale (voiced by Helena Bonham Carter):
Similar diagrams might be constructed for towns in their unimproved and improved state. Nature is the same everywhere and never permits her laws to be disregarded with impunity.

Tim Harford:
The argument is powerful, and the conclusion is correct. Life expectancy strikingly improved in the second half of the 19th century, and the sanitarian revolution, cleaner water, cleaner homes, cleaner air deserves much of the credit, but that’s why it’s so shocking to see the data from the Rose Diagram replotted as a bar chart. When you do that, the stark before and after story is lost. By the time the sanitary commission arrived in March, flushing horses out of the water supply and carrying away tons of human excrement, deaths had already been falling sharply for a couple of months.

Tim Harford:
Mark Bostridge, the author of an award-winning biography of Nightingale, argues that deaths were falling because new arrivals were in better health, in part, thanks to the better weather. They were less numerous, so the hospital was less overcrowded. And with fewer soldiers in the hospital, of course, there’d be fewer deaths. There’s no doubt that better sanitation works, but an unvarnished presentation of Nightingale’s data would have suggested that the truth was complicated, and complicated wasn’t going to serve her purposes. So she created her Rose Diagram. The same data artfully presented tells a very different story. There’s a famous remark in a letter that passed between Nightingale and her ally, the great statistician William Farr.

Voiceover:
You complain that your report would be dry. The drier the better, statistics should be the driest of all reading.

Tim Harford:
Several biographers have reported that remark as being written by Farr to Nightingale. That makes sense. The fusty, middle-aged statistician was advising the fiery younger advocate to reign in her righteous campaigning influences, and thankfully she ignored him. Except, the biographers are wrong. Confused perhaps by the fact that the surviving draft of this letter was dictated to an assistant and unsigned. But while researching my new book “The Data Detective,” I tracked the letter down, and it wasn’t from Farr to Nightingale, it was the other way around.

Florence Nightingale (voiced by Helena Bonham Carter):
You complain that your report would be dry. The drier, the better. Statistics should be the driest of all reading.

Tim Harford:
She was telling him to play it straight and avoid editorializing. Solid evidence first, she said and worry about the sales pitch later. Good advice for any scientist. In the same letter, she added:

Florence Nightingale (voiced by Helena Bonham Carter):
We want facts. Factor, factor, factor is the motto which ought to stand at the head of all statistical work.

Tim Harford:
It’s puzzling. How could she produce the famous rose diagram, an artfully constructed piece of statistical storytelling, while being the same person who told William Farr to keep it dusty dry? My guess is that she was far too clever to build an argument on shaky foundations. The more spectacular the statistical acrobatics, the more solid the numbers needed to be. But it’s just a guess, I don’t know.

Tim Harford:
I don’t even know if this cautionary tale has a happy ending. If the end justifies the means, I suppose it does, because she won. Nightingale and her allies saved countless lives, transforming the health of Victorian Britain and arguably of the world. Most of Nightingale’s campaigning took place while she was confined to her bedroom by the long illness she had acquired in Crimea, and she emerged triumphant. Germ theory had vindicated her focus on hygiene and public health. Her sanitarian reforms had been broadly implemented. The everyday health of ordinary citizens had been transformed. Even Dr. John Simon, it seems, had quietly recognized his mistake. He published a collection of his essays, and without acknowledging the change, he altered the line that said that deaths from disease were.

Voiceover:
Practically speaking, unavoidable.

Tim Harford:
Instead, saying they were-

Voiceover:
In some degree, unavoidable.

Tim Harford:
From saying, ‘there’s nothing we can do to save lives,’ john Simon had softly sidestepped into saying, ‘well, we can’t save everyone.’ Florence Nightingale and her Rose Diagram had defeated him. But let’s be careful because it seems that if you give us 500 milliseconds alone with a pretty graph, we’re all suckers. The first data visualization to change the world did so by exploiting our visual gullibility. Florence, Nightingale’s beautiful graphic proved a powerful weapon, and now it’s a weapon that anyone with any motive can pick up and use.

Tim Harford:
Key sources for this episode include Mark Bostridge’s biography and Lynn McDonald’s collected works of Florence Nightingale, Hugh Small’s presentation to the Royal Statistical Society and my own book, ”The Data Detective: 10 Easy Rules to Make Sense of Statistics. For a full list of references, see Timharford.com. Cautionary Tales is written by me, Tim Harford with Andrew Wright. It’s produced by Ryan Dilley and Marilyn Rust.

Tim Harford:
The sound design and original music is the work of Pascal Wyse. Julia Barton edited the scripts. Starring in this series of Cautionary Tales are Helena Bonham Carter and Jeffrey Wright alongside Nesar Eldarasi, Ed Gaughan, Melanie Gutteridge, Rachel Hanshaw, Kobna Holdbrook-Smith, Greg Lockett, Mircea Monroe, and Rufus Wright. This show wouldn’t have been possible without the work of Mia Lobel, Jacob Weisberg, Heather Fain, Jon Schnaars, Carly Migliori, Eric Sandler, Emily Rostek, Maggie Taylor, Daniella Lakhan, and Maya Koenig. Cautionary Tales is a production of Pushkin industries. If you like the show, please remember to rate, share, and review.

Roman Mars:
The new season of ‘Cautionary Tales’ is out now. Go subscribe and listen. I love the show. I’m so happy it’s back, and then once you’ve subscribed, go buy all of Tim Harford’s books because they’re fantastic. The latest one is called “The Data Detective: 10 Easy Rules to Make Sense of Statistics.”

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Roman Mars:
99% invisible is a product of 91.7. KALW in San Francisco and produced on Radio Row in beautiful downtown Oakland, California. You can find the show and join discussions about the show on Facebook. You can tweet me at Roman Mars and the show at 99pi.org. We’re on Instagram and Reddit, too, but our home for beautiful nerds is 99pi.org.