Microsoft founder turned philanthropist Bill Gates predicts that by 2035 there will be almost no poor countries left.
He said Africa was a far better place than 50 years ago, but work had to continue to uplift the continent.
On Tuesday, the Bill and Melinda Gates Foundation released Mr Gates’s annual letter in which he talks about three myths that block progress for the poor.
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They are that poor countries are doomed to stay poor, that foreign aid is a big waste, and that saving lives leads to overpopulation.
Usually the foundation’s annual letter focuses on its work and programmes for the coming year.
However, in this year’s letter Mr Gates said these three "myths" were blocking progress for developing nations and aid had actually helped reduce poverty levels, spurred development and helped improve the lives of billions of people.
In fact, he said, aid had been so successful in helping developing countries to uplift themselves that: "I am optimistic enough about this that I am willing to make a prediction. By 2035, there will be almost no poor countries left in the world…. Almost all countries will be what we now call lower-middle income or richer.
"Countries will learn from their most productive neighbours and benefit from innovations like new vaccines, better seeds, and the digital revolution. Their labour forces, buoyed by expanded education, will attract new investments."
More specifically, Mr Gates said he meant that by 2035, almost no country would be as poor as any of the 35 countries that the World Bank currently classifies as low-income, even after adjusting for inflation.
He said the easiest way to respond to the myth that poor countries were doomed to stay poor was to point to one fact: they have not stayed poor. He said many - though by no means all - the countries we used to call poor now had thriving economies and the percentage of very poor people had dropped by more than half since 1990.
That still left more than a billion people in extreme poverty, however, "so it’s not time to celebrate. But it is fair to say that the world has changed so much that the terms ‘developing countries’ and ‘developed countries’ have outlived their usefulness."
Any category that lumped China and the Democratic Republic of Congo together confused more than it clarified, he said. Some so-called developing countries had come so far that they could be deemed to have developed, while a handful of failed states were hardly developing at all.
Mr Gates said most countries were somewhere in the middle, and it was more instructive to think about countries as low-, middle-, or high-income.
Mr Gates disputed the "myth" that Africa was worse off today than it was 50 years ago.
Per-capita income had in fact risen in sub-Saharan Africa over that time, and quite a bit in a few countries. After plummeting during the debt crisis of the 1980s, it had climbed to nearly $2,200 from just over $1,300 in 1998. Seven of the 10 fastest-growing economies of the past half-decade are in Africa.
Africa had also made big strides in health and education, he said.
Since 1960, the life span for women in sub-Saharan Africa had risen from 41 to 57 years, despite the HIV epidemic. Without HIV it would be 61 years.
The percentage of children in school has increased from the low 40s to more than 75% since 1970. Fewer people are hungry, and more people have good nutrition.
"If getting enough to eat, going to school and living longer are measures of a good life, then life is definitely getting better (in Africa). These improvements are not the end of the story; they’re the foundation for more progress," Mr Gates said.
He said foreign aid was not a waste as it had helped reduce child mortality rates from 16 per 100 000 to about five per 100 000. Aid did not create dependency but helped poor people focus on improving their situation.
Mr Gates said aid would not lead to overpopulation since improving child mortality rates were accompanied by corresponding declines in birth rates.