How has wellbeing evolved over time and across regions? How does the West compare to the Rest? What explains their differences? These questions are addressed using a historical index of human development. A sustained improvement in world wellbeing has taken place since 1870. The absolute gap between OECD and the Rest widened over time, but an incomplete catching up—largely explained by education—occurred between 1913 and 1970. As the health transition was achieved in the Rest, the contribution of life expectancy to human development improvement declined and the Rest fell behind in terms of longevity. Meanwhile, in the OECD, as longevity increased, healthy years expanded. A large variance in human development is noticeable in the Rest since 1970, with East Asia, Latin America, and North Africa catching up to the OECD, and Central and Eastern Europe and Sub-Saharan Africa falling behind.