Max Roser in Our World In Data:
To avoid portraying the world in a static way – the North always much richer than the South – we have to start 200 years ago before the time when living conditions really changed dramatically.
Researchers measure extreme poverty as living with less than 1.90$ per day. These poverty figures take into account non-monetary forms of income – for poor families today and in the past this is very important, particularly because of subsistence farming. The poverty measure is also corrected for different price levels in different countries and adjusted for price changes over time (inflation) – poverty is measured in so-called international dollars that accounts for these adjustments.
The first chart shows the estimates for the share of the world population living in extreme poverty. In 1820 only a tiny elite enjoyed higher standards of living, while the vast majority of people lived in conditions that we would call extreme poverty today. Since then the share of extremely poor people fell continuously. More and more world regions industrialised and thereby increased productivity which made it possible to lift more people out of poverty: In 1950 three-quarters of the world were living in extreme poverty; in 1981 it was still 44%. For last year the research suggests that the share in extreme poverty has fallen below 10%.
More here.