The 2010s have been the best decade ever. The evidence is overwhelming. Start with the United Nations Development Report. Framed as a warning about inequality, it plays down the good news: “The gap in basic living standards is narrowing, with an unprecedented number of people in the world escaping poverty, hunger and disease.”

The World Bank reports that the world-wide rate of extreme poverty fell more than half, from 18.2% to 8.6%, between 2008 and 2018. Last year the World Data Lab calculated that for the first time, more...