information even if it doesn’t quite fit the question. Our huge overestimates of the rural populations in most countries will be affected by how much of the physical landmass rural areas make up, rather than a careful calculation of how unoccupied it generally is. In Daniel Kahneman’s terms, answers to these sorts of questions are classic examples of “fast” thinking, rather than “slow”. We are tied to our own perspective and struggle to imagine the variety in our countries, as highlighted by our Indian sample’s massively overestimating their population’s access to the internet. Our study was mostly carried out through an online survey – and, in developing countries, this will be representative of a more affluent, connected group rather than the population as a whole. In some ways, we may have expected this more educated sample to get closer to reality – those with higher education levels tend to be more accurate on these types of questions. But what we find, throughout the study, is that people grossly generalize from their own situations, forgetting how unrepresentative they are. We suffer from what social psychologists call “emotional innumeracy” when estimating realities: this means we are sending a message about what is worrying us as much as trying to get the right answers. Cause and effect run both ways, with our concern leading to our