The world can be a confusing place. We’re constantly bombarded with facts and figures, infographics and images. They appear to us in the news, in magazines, and on social media. This is all supposed to inform us — the authors are certainly trying to persuade us of something. Yet a lot of this information is confusing, contradictory, and imperfect. How can we make all of this add up?
Thankfully Tim Harford is here again to help demystify things for us. In his latest book he presents us with ten rules for navigating this confusing world of numbers. The rules range from remembering to check our emotional responses to information, to reminding us to look for the full story behind the figures we are presented with. Throughout, he emphasises the values of healthy scepticism and scientific curiosity, and the importance of staying open-minded. The book is framed differently to Darrell Huff’s How to Lie with Statistics — in fact, Harford finds Huff’s pessimism unhelpful. The solution isn’t to dismiss statistics as lies, or to get sucked into a state of extreme scepticism about every number — it’s to better navigate the world of numbers to discern the good from the bad, and the plausible from the improbable.
Harford explains his ten commandments with characteristic wit and storytelling flair. There is a mix of historical narrative, which serves as an allegory for the deeper message he’s trying to convey, with an exploration of notable scientific studies that explain the point in more detail. Some of the stories he recalls may well be recognisable to the reader — there were several that I’ve come across before — but their impact won’t be less for their familiarity. Readers may well know the importance of Florence Nightingale, or the misfortunes of Irving Fisher, but the retelling of their stories is useful — it helps take the reader on a journey. Harford also draws on several other works likely to be familiar to the reader, integrating other arguments effectively. Readers of Kahneman’s Thinking, Fast and Slow, or Tetlock’s Superforcasting will recognise some of the ideas present here. Yet Harford is able to draw on his own learnt experience to create a compelling synthesis. The result is plenty of solid advice for dealing with numbers, uncovering their meaning, and looking beyond what is presented to you in the media.
The book isn’t perfect. There is a tendency to assume that things like political polarisation can be solved through a pure, rational approach to good evidence. While that would surely help, Harford doesn’t show much appreciation for the part played by intrinsic values, first principles, or personal priorities in guiding people’s biases or political persuasions. The result is an oversimplification in places. If someone values freedom over safety, showing them good statistics or better facts on gun violence is unlikely to shift their position because it doesn’t speak to their core values. In the first chapter, for example, Harford chalks up this kind of division to simple emotionality. To Harford’s credit, in later chapters he does stress that the reader should be sceptical even of the articles that he cites (which would include the ones that ‘show’ that division is driven by emotion); he also mentions that “deep ethical questions” can be the cause of division later on. This kind of self-awareness would have been valuable elsewhere, too.
The main strength of this book is its easy-going, conversational style. It means that the advice comes through well, and that Harford comes across as sincere, genuine, and well-meaning. The writing flows nicely, and I managed to get through the book (and absorb its message) with ease. Harford tells several stories simultaneously within the same chapter, often using the historical example as a narrative thread, interspersing scientific studies from fields like psychology and behavioural economics to drive the message home. This method is effective, informative, and entertaining. It adds to a burgeoning literature that makes statistics accessible to laypeople, and it would make a great companion or follow-up to something like Sir David Spiegelhalter’s The Art of Statistics, which is a little more to the academic side of the statistics-infotainment spectrum. Readers of both will find some important points echoed across these books. For people who want to feel more control over the information that they are presented with, How to Make the World Add Up comes highly recommended.
Tim Harford, How to Make the World Add Up: Ten Rules for Thinking Differently About Numbers (London: The Bridge Street Press, 2020), pp. 352.
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Bucky Unbound 
Really great review! I agree with your point about being sensitive to people’s values and principles. I feel like there’s a lot of psychology hidden behind this; people tend to see/understand what they already think. Without understanding people’s values, these can be meaningless numbers with no context. It’s another reason why telling a story with data is so important for data analysts to do.
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Yes, exactly! And he does go into a lot of behavioural science that does try to deal with it. I disagreed with some of the analysis principally because it ignored a lot of the philosophy of why people believe things, and was a bit reductive. But yes, telling a story with data and thinking carefully about what the numbers represent is so important.
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