How do we know the history of extreme poverty?

Joe Hasell and Max Roser:

The poverty researcher Martin Ravallion spent decades researching how poverty can be measured and which policies can help us in our fight against poverty. The summary of his work is his monumental book ‘The Economics of Poverty: History, Measurement, and Policy’.

The first chapters of this book present a detailed history of global poverty and how the research of poverty has developed. The very big-picture of the long-run decline of extreme poverty he summarizes in the following figure. The chart shows that the share of the world population living in extreme poverty declined continuously over the last two centuries.

What is this chart based on? How do we do know that just two centuries ago the majority of the world population lived in conditions that are similar to the living conditions of the very poorest in the world today as this chart indicates? And how do we know that this account of falling global extreme poverty is in fact true?

It is the research of hundreds of historians who have carefully assembled thousands of quantitative estimates that inform us about us about people’s living conditions that give us this global perspective on the history of poverty.