Eight economists, including a number of Nobel Prize winners, wrapped up on Saturday the week-long Copenhagen Consensus conference, at which they were asked to prioritise how to spend an imaginary extra $50 billion to improve the world.
The panel gave the highest priority and $27 billion to combating HIV/Aids because of its humanitarian urgency, in particular in Africa.
"Although costs are considerable, they are tiny in relation to what can be gained," the group said in a statement. The Aids virus has infected 43 million people globally and has killed more than 25 million.
Hunger was ranked as the second most important problem and the panel wanted to spend $12 billion to fight malnourishment, especially among children.
The experts were invited by Bjorn Lomborg, the Danish author of The Sceptical Environmentalist and director of the Environmental Assessment Institute think-tank who is a bete noire for traditional "greens" worried about global warming.
The panel was faced with 10 challenges: Climate change, diseases, hunger, migration, sanitation, corruption, trade barriers, education, conflicts and financial instability.
It ranked 17 solutions to seven of the challenges - finding there was insufficient information on the other three problems.
"Everyone would love to address all the problems if there was enough money. But as long as money is a scarce resource we have to focus on where should we do most good first"
Author of "The Sceptical Environmentalist"
However, it decided to assign money only to the four most urgent issues.
"That encapsulates the big dilemma. Everyone would love to address all the problems if there was enough money. But as long as money is a scarce resource we have to focus on where should we do most good first," Lomborg told a news conference
As in a parallel ranking by 80 students from 25 countries, the economists gave low priority to climate change, which many scientists say could be the most serious long-term threat to life on the planet.
The students ranked the issue as number nine out of 10, while the economists ranked it 16 out of the 17 proposed solutions.
"This issue is not whether climate is important but how timely it is to devote many resources to that at the present time, given these other very serious and pressing and urgent problems that need action," said 2002 Nobel Prize winner Professor Vernon Smith from George Mason University.
Meanwhile, free trade came in at number three.
"Trade liberalisation is globally welfare-increasing, especially in the developing countries, so we couldn't resist the temptation of putting it on the list even though it's not a candidate for spending money," said Professor Thomas Schelling from the University of Maryland.
Control and treatment of malaria, believed to kill more that a million people a year, was ranked fourth and given $13 billion.
Dangers to the environment
ranked low on the experts' list
The panel did not make clear why their total overran the $50 billion budget.
The economists said they did not expect their list to be used by politicians as an answer book, but said their mission was to provide better and more developed information for people to make their own judgments.
Some environmentalists have criticised the makeup of the panel, saying some of the economists were not experts in the fields under discussion. But Lomborg has defended the panel as even-handed.