Population ageing will continue to be one of Europe’s biggest long-term policy challenges in coming decades. Older populations have many advantages, but they also have very concrete costs—most notably on pensions, one of the foundations of modern-day welfare states. Longer lives, the result of better health and nutrition, is certainly part of the equation, but this can hardly be qualified as a problem. No, Europe is ageing, and—despite our intentions—low fertility is the reason. Low fertility is also the result of positive developments.