Concerns about declining or ageing populations often centre on the fear that fewer people will translate to a weaker economy and lower living standards. But these fears are frequently based on oversimplified or misapplied interpretations of economic models, and appear to be driven more by political agendas rather than evidence. In reality, long-term prosperity depends more on how societies invest in education, skills, and technology, not just how many people they have. We examine national dat...