More or Less: Behind the Stats

It's the last in the series so we're packing in the statistical goodies so that you can go into numerical hibernation until August. We're looking at the street value of drugs: when police claim that they've confiscated hundreds of millions of pounds worth of narcotics, where do those numbers come from? And how has the dark internet changed drug prices? We'll also be looking at claims that those of us who aren't binging on drugs are binging on biscuits instead. Apparently much of the UK and almost the entire population of Ireland is going to be obese before long. But how have such alarming forecasts fared in the past? We're often told that we consume so much that we need one and a half planets - and not just to provide room for all those obese people. What does that number even mean, and is it helpful? And Richard Thaler, the co-author of "Nudge", joins us to talk about the psychology of risk.