Some weeks ago, I had the honor to talk an hour with Alberto Cairo. He had some very interesting things to say about journalism and about visual literacy and learning to code. But I didn't want to waste the opportunity to ask him about his favorite visualizations.
What is your favorite visualization?
Alberto Cairo: John Snow's map of the cholera outbreak. That is is my all time favorite. Because it tells us so many things about what visualization is about. And not only visualization: also what good epidemiology is about, what data journalism is about.
'The nicest thing about that graphic is the background, what happened before the visualization. Snow worked as a data journalist. He didn't just create the graphic to 'prove' something. He didn't stop at only looking on the trend, you know: the closer you are, the higher the number. No, he also focused on the exceptions. There was a person over here and a person over there who died but lived far from the well. He went to these houses to see why! That is a data journalist.
'It is an excellent example of how data journalism should work. And it is obviously one of the main historical changes in epidemiology. That is my absolute historical favorite, because of the story behind it.'
And what would be the most impactful visualization?
Alberto Cairo: 'I write about that in my new book. The second chapter of the book begins with a blogpost by Enrico Bertini, Do we really know if visualizations make a change?. So my second chapter opens with Enrico's question, and I say: 'Yes.' Every time someone discovers something useful thanks to a graphic, that is an example of success. And I give several examples.
'On top of my head, the first one that I remember is of a graphic that changes you the moment you see it. Obviously, John Snow's cholera map is an example of that, but a more modern example is the Hockey Stick Chart. Have you ever seen that one? It is a graphic about global temperatures.
'It was created back in the nineties by a group of climate scientists led by Michael Mann. It was published in the IPCC report in 1999. It is one of the most successful visualizations ever created, because you see it and you cannot fail to see the evidence that there is something going on in the 20th century. Al Gore showed it in his An Inconvenient Truth.
'The graphic created a huge controversy. The people in the fuel industry and all the morons that basically deny the evidence for climate change got scared. Because the graphic is so extremely persuasive. And they started attacking people like Michael Mann personally. They tried to destroy his reputation. But he survived all these attacks and ended up writing a book about the whole discussion: The Hockey Stick and the Climate Wars.
'He and his colleagues were attacked just because of the graphic. It was the graphic that created the controversy. That is probably the most successful modern visualization in my opinion, because it can change lives. But there are plenty of examples of impactful visualizations out there.
'Another example is the the graphic that I showed this morning [in his keynote for the NTTS2015 conference], about measles in the US.
The measles graphic by the Wall Street Journal.
'What can you say about vaccines after you've seen that graphic? You cannot deny that they are useful and that they work. They do work: take a look at the data. You cannot fail to see it.
I don't mind that there are a lot of bad visualizations, as long as the amount of good visualizations also increases.
'The more people that start creating visualizations, the more examples we will see. We will also see the amount of crap increase, that is obvious. But as Theodore Sturgeon said many years ago: '90 percent of everything is crap.' If you increase the amount of things, you will have more crap, but you will also increase the 10 % of great things, which is what everyone wants. I don't mind that there are a lot of bad visualizations, as long as the amount of good visualizations also increases.
'And that is what we are seeing nowadays: an increase of great visualizations. Done in many cases by people who are not professional journalists or professional visualization designers. They are people just tinkering with Tableau, D3 and other tools. That is a wonderful trend for the future. And we need to support that, we need to praise these people.
'Let me give you an example. A few months ago the New Republic Magazine, a weekly magazine in the US, they published a story on their website about Medicaid. The story was that several states in the US are refusing to expand Medicaid and people are losing money because of that. Well, the New Republic rolled the story and the story included two choropleth maps in which you can see the amount of money that each state is losing. The original version of the map was really bad, whit a lot of colors.
The original version of the Medicaid map.
'When the author of the story tweeted it, I said: 'You know, this map isn't very good. Maybe you want to use a completely different color palette.' And then the guy replied to me, saying that he was sorry, because it was the first time he did a visualization. So he was a writer, a reporter, and he said: 'I need to create a map for this story.' But there was nobody around that could help me. So he went online and he found Datawrapper. And he created a wonderful visualization with it: he created a map.
'I want to see more examples of that. Every time I see someone who never created a visualization before making one and publishing it, I will praise that person if the visualization is informative. And when the graphic is not very good, I will praise that person and than give some advice on how to improve their work, because people appreciate that. They will feel prompted, invited to create more visualizations.
The revised version.
'So the guy from the New Reporter changed the map, based on comments from me and another cartographer. I want more stories like that. People should just try and they will see that is not magic. It is actually easy to do.'