During the 180 years from 1820 to 2000, world output per person increased roughly eleven times, leading to an equally dramatic fall in the global rate of extreme poverty—from around 90 percent in 1820 to roughly 10 percent as of 2015.

Considerable development took place in the decades after World War II and, more recently, following the end of the Cold War. The proportion of people living in extreme poverty (defined as those living on less than $1.90 per day) is down from 40–50 percent of the world’s population fifty years ago and more than one-third of the population as recentl