Early in their latest book, Think Like A Freak, Stephen J Dubner and Steven D Levitt introduce their readers to a rare but wonderful term: "Ultracrepidarianism, or 'the habit of giving opinions and advice on matters outside of one's own knowledge or competence'."
It's a risky topic for the authors of Freakonomics, who could be accused of displaying ultracrepidarian tendencies themselves, after eschewing the strictly economic analyses of their earlier mega best-sellers to publish what is more or less a self-help tome.
Think Like A Freak explains how the average non-economist might approach problems, so as to reach the sort of counterintuitive conclusions that characterised 2005's Freakonomics, which linked plummeting crime rates to the legalisation of abortion; and 2009's follow-up, SuperFreakonomics, which explained why terrorists rarely have life insurance policies.
The new book is full of common-sense instructions: tackle small problems, not vast ones; identify a problem's root cause, not just the symptoms; don't be too proud to quit. It's illustrated with colourful stories, such as how a slim Japanese man became a world champion hotdog eater; how Chinese schoolchildren's grades were improved not with teaching reforms, but with free eyeglasses; and why David Lee Roth, of Van Halen, and King Solomon were both game theorists.
"After the first book," says Levitt, "we believed people wanted great stories built on economics, and that they would love stories about problems that were material to the future of the world, like climate change and terrorism. But after the second book, we realised that wasn't it: what people really loved about us was that we had a different way of approaching the world, and we were problem-solvers. The point of this book was to say: let's show them how the magic works."
In the decade since they published their debut, the publishing genre that Dubner and Levitt pioneered – let's call it story-based social science – has become increasingly crowded. Several critics have suggested that the Freakonomics brand has outstayed its welcome, with one comparing Think Like A Freak to "the sound of scraping the bottom of a barrel Malcolm Gladwell has already rummaged through". But the authors are unperturbed.
"Nobody likes everything, and the more public you get the more you have to deal with that," Dubner says. "I sometimes look at negative criticism to see if it's helpful, but whatever we do next is not going to be determined by some cranky journalist who says we should stop for whatever reasons he might have – including that maybe he wants us to get off the stage so that he can get on."
Dubner and Levitt first met as interviewer and subject when Dubner was a journalist for the New York Times and Levitt an iconoclastic economist at the University of Chicago. Today they preside over a Freakonomics empire of films, podcasts, public speaking and private consultancy. Dubner is talkative and enthusiastic, Levitt thoughtful and somewhat more subdued. They both wear expensive-looking designer specs, the only visible fruits of their vast success.
Asked to name a measurable impact that their work has had on the real world, they merely shrug and point to the post-Freakonomics boom in undergraduate economics students. When pressed, Dubner also mentions that they once called on New York City to introduce a dog DNA database in order to track down on dog owners who failed to scoop their pooch's poop. The plan was eventually taken up – not in New York, but in Petah Tikva, a town near Tel Aviv in Israel.
Ridding urban streets of the scourge of dog faeces may be an admirable goal, but the two men also have loftier aspirations. Before writing Think Like A Freak, Levitt co-founded a group of big thinkers called The Greatest Good, with a view to tackling major global problems such as obesity, addiction and access to clean toilets in the developing world.
"The idea was to come up with a list of the 50 biggest problems that we might actually be able to solve," he explains. "Many billionaire philanthropists are bullied by society or by other billionaire philanthropists into saying they'll give away a large chunk of their money, but they don't have a vision. We thought this white paper would be something we could put in front of them and say, 'Here's 50 solvable problems', and they could choose which ones to work on."
Levitt says that he had hoped that former New York Mayor Michael Bloomberg might run for the US Presidency and use the list as a manifesto. Another politician who took note of Freakonomics was David Cameron, who once solicited the authors' advice.
In the first chapter of Think Like A Freak, Dubner and Levitt recall a meeting with the then British Opposition leader shortly before the 2010 general election. After a pleasant afternoon at Conservative HQ, the pair were introduced to Mr Cameron, who, Dubner says, told them: "I'm about to get elected, the budgetary situation is crap and I have to look for something to cut. But there are some things I won't cut, like the NHS."
Misjudging the chummy atmosphere, the two men suggested that perhaps the health system wasn't such a special case after all, and that a Cameron government ought to consider treating it like any other overspending department – like transport, for example. Cameron, they write, "offered a quick handshake and hurried off to find a less ridiculous set of people with whom to meet". And yet, Dubner says now, "The irony is, he has cut the NHS!"
Levitt first learned to think "like a freak" as an economics postgraduate. "In graduate school I was on a constant hunt for interesting ideas and I became attuned in a very predatory way: I'd look at everything and ask myself, 'could that be an economics paper?'" He found his pet subject – crime – after long hours spent watching the reality show Cops. "Criminology journals always gave me enormous amounts of ideas," he says, "because criminologists asked lots of really interesting questions, but they didn't approach them the same way that an economist would."
Reading the new book, one might assume that thinking "like a freak" is only effectual when applied to small but identifiable problems – such as how to eat a lot of hotdogs very quickly. But Levitt disagrees. "With huge, complex problems, nobody ever makes progress by taking on everything at once. The story of the eyeglasses for schoolchildren in China is a perfect example of how if you take a problem that's big, like education, but you carve out a small piece, you can still have an enormous impact – even though you've only tackled 2 per cent of the problem. Two per cent of something huge is better than no per cent."