AbstractThis paper uses data for 134 countries for the period 1960–2010 to document an energy ladder that nations ascend as their economies develop. On average, economic development results in an overall substitution from the use of biomass to energy sourced from fossil fuels, and then increasingly towards nuclear power and certain low-carbon modern renewables such as wind power. The process results in the carbon intensity of energy evolving in an inverse-U manner as per capita incomes increase. Fossil fuel-poor countries climb more quickly to the low-carbon upper rungs of the national-level energy ladder and so typically experience larger reductions in the carbon intensity of energy as they develop. Leapfrogging to low-carbon energy sources on the upper rungs of the national-level energy ladder is one route via which developing countries can reduce the magnitudes of their expected upswings in carbon dioxide emissions.