A good economic bet

Two economists disagree about the state of the economy. That’s not terribly surprising; you can insert your own joke here. Refreshingly, they’ve decided to put money on the table: instead of spouting hot air, they have made a bet. Bravo. More public intellectuals should follow suit.

Jonathan Portes is director of a UK think-tank, the National Institute for Economic and Social Research. Andrew Lilico runs Europe Economics, a consulting firm. Portes thinks that there’s plenty of spare capacity in the British economy, and that even as economic growth picks up, inflation will remain modest. Lilico disagrees. The men have staked £1,000 – inflation-adjusted, naturally.

The bet says (roughly) that once economic growth tops 2 per cent in the UK, inflation will exceed 5 per cent within 18 months. Economic growth has indeed picked up, so the bet is on and the clock is ticking. By October 2015 we should have a winner.

There is a long-running debate about whether this sort of wager is to be welcomed. Alex Tabarrok, an economics professor at George Mason University, is all in favour. “A bet is a tax on bull****,” he wrote after statistical journalist Nate Silver offered a wager on the results of the 2012 presidential election, with profits to go to charity. The New York Times public editor, Margaret Sullivan, disagreed. Silver was writing for the newspaper back then, and Sullivan declared it was “inappropriate” for journalists to be publicly wagering that their opinions were well founded.

Who’s right? Sullivan’s main argument against Silver’s wager was that it created the “appearance” of a conflict of interest. Albeit indirectly, Silver stood to profit from a victory for the Democratic Party, if only by avoiding having to make a charitable donation. Suddenly he was no longer disinterested. This is a shallow foundation for the case against public wagers.

And there are strong counter-arguments. Pundits who make wagers may look grubby but at least they are accepting a cost for failure. A more subtle advantage is that betting encourages forecasts that are specific and quantifiable.

This matters, because too many forecasts are both vague and consequence-free. A pundit can shoot his mouth off about what will happen in the future and nobody much cares. If the forecast should happen to come true, the pundit can revisit his words and claim to have predicted the financial crisis, the fall of the Berlin Wall or whatever. What’s more, many forecasts are hazy enough, especially on timing, to make them impossible to falsify.

Making a wager helps correct both these problems. A forecast that is specific enough to bet on is also specific enough to come true, or to fail. And for any wager, there is at least one person with an incentive to keep track of what happened.

The most famous bet about economics is that between Paul Ehrlich, ecologist, doomsayer and author of the massive 1968 bestseller The Population Bomb, and Julian Simon, an economist most famous because he persuaded Ehrlich to bet with him. Ehrlich believed that overpopulation would cause disaster and widespread scarcity. Billions would die, developed countries would disintegrate, India was beyond saving. Simon thought that people would find substitutes for scarce resources and that things would be fine.

The bet, however, needed to revolve around something specific. It was that the price of five metals would rise between 1980 and 1990 as scarcity continued to bite. Instead prices fell, dramatically. Ehrlich lost the bet. In some ways, this story shows the value of the wager. Because the bet was specific, we now know that Ehrlich was wrong and Simon, who died in 1998, was right.

Yet the tale of the Ehrlich-Simon bet is not entirely reassuring. The very fact that the bet was so specific means that long after Simon won, the argument continues to rage about whose worldview was truly correct. I have never met an environmentalist who was convinced by Simon’s victory that technology will save the world. And I have encountered many conservatives who seem to believe that because Paul Ehrlich was wrong about the price of metals in the 1980s, all environmentalists are wrong about everything.

Paul Sabin, a historian who wrote a book about the bet, argues that the affair brought more heat than light. He reports that Ehrlich took his loss with poor grace, sending Simon a cheque with no cover note. And Ehrlich seems unrepentant. In a recent interview with NPR’s Planet Money show, he said of the late Simon, “It’s hard to be more wrong… he knew absolutely nothing about anything important.”

This pigheadedness is disheartening but unsurprising. Perhaps the wager pushed each side into stubborn tribalism and encouraged a reductive view of complex affairs.

Yet on balance, the world needs more wagers between pundits. The alternative is intolerable: a world full of confident forecasts that nobody ever bothers to verify. The betting man must be thoughtful and specific or his wallet will suffer the consequences. We should all be quicker to ask ourselves before we open our mouths: would I be willing to bet on this?

Tim Harford’s new book, “The Undercover Economist Strikes Back”, is out in paperback on July 3

Twitter: @TimHarford

Illustration by Harry Haysom