Classical economic theory rests on the assumption that individuals act rationally and in their own self-interest — an assumption (0) UPON which entire policy frameworks have been constructed. Behavioural economists have, 1, demonstrated that human decision-making is far less rational than traditional models suggest. People routinely make choices that are against 2 own best interests, influenced by cognitive biases of which they are largely unaware. So pervasive 3 these biases that even trained economists have been shown to fall prey to them in their personal financial decisions. It was not until the work of Kahneman and Tversky in the 1970s 4 the discipline began to take such irrationality seriously. Had their research 5 published a generation earlier, the field of economics might look very different today. Not 6 did their findings challenge the foundations of economic theory, but they also had profound implications for public policy. The concept of ‘nudging’ — designing choices in 7 a way as to steer people towards better decisions without restricting their freedom — owes its existence to their pioneering work. Controversial 8 the practice of nudging may be, governments around the world have embraced it with enthusiasm.