“The poor may well be living in remote areas or low income areas well away from the capital or large cities. They may also be in social groups that are discriminated against or there may be internal regulations or substantial costs of migrating across the country,” he said.

Sumner said half of the world’s poor live in India and China; one quarter live in heavily populated middle income countries, such as Nigeria, Pakistan and Indonesia. The rest are in low income countries.

“If you look over the last 20 years, although at a global level the proportion of the world’s population in poverty has fallen a lot, it’s actually about the same in absolute numbers, partly because of population growth,” he said.

But where will the world’s poor live in 2020 or 2030? Sumner said that half of the world’s poor could still be in middle income countries. He warns that figure could rise if the gap between the haves and have-nots continues to widen.

He estimated the cost of eliminating extreme poverty to be about 60 to 80 billion dollars a year. That’s about 0.3 percent of the world’s GDP, or gross domestic product, which is the value of final goods and services produced in countries.

Sumner said that with the “distribution of global poverty away from the poorest countries to middle income countries, a new approach to understanding and tackling extreme poverty is required.” He added that this includes a more equitable distribution of the “benefits of economic growth and public spending…on the chronic, long-term poor wherever they live.”