Until 1950, this had always been less than 2 percent per year, before leaping to 4 percent in the period 1950–1990, an exceptionally high level that reflected both the highest demographic growth rate in history and the highest growth rate in output per head. The rate of growth of global output then began to fall, dropping below 3.5 percent in the period 1990–2012, despite extremely high growth rates in emerging countries, most notably China.
