(FORTUNE Magazine) – It is October 2007, and the U.S. presidential elections are just over 12 months away. In a TV studio's green room, a presidential hopeful practices her lines: "As the sole superpower, the U.S. has a moral responsibility to raise living standards around the globe. I pledge to focus our nation's foreign aid budget on improving education in developing nations. My reasoning is both idealistic and pragmatic. First, we all know that education provided the basis for the American Dream. But second, we know that spending on education provides value for money."

Across the Atlantic in the House of Commons, unusually reasonable political discourse is also taking shape. Amid heckling from both sides of the chamber, the leader of the opposition demands to know: "Where are this government's priorities when it is spending an extra £50 million to slow global warming--money that all evidence shows could better be spent providing clean drinking water to developing nations?"

In 2004 we seldom hear well-informed debate about the money spent around the world to raise living standards. If we hear such discussion at all, it's in response to television pictures of the latest outbreak of human suffering: "Surely we should spend more money on that!" Yet we do not ask ourselves--as the hypothetical enlightened politicians of 2007 do--how we could use our money to provide the most good for the greatest number of people.

It's not that the world hasn't figured out lists of problems to solve. The United Nations, for example, has its worthy Millennium Development Goals. ("Achieve universal primary education" and "Promote gender equality and empower women" are examples.) These goals aren't cheap. The World Bank estimates that additional foreign aid of between $40 billion and $70 billion (vs. some $57 billion today) will need to be spent each year until 2015 to achieve the UN's goals.

What the world does have a shortage of is prioritized goals. What do we do first? And then what? If we had an extra, say, $50 billion to spend tomorrow, should we focus on trying to ensure that all children complete a full course of primary schooling, or should we direct our attention to eliminating sexist disparity? Where would the money do the most good?

A new project called Copenhagen Consensus has undertaken the task of creating a kind of global to-do list to put prioritization on the agenda, and bring the hypothetical political debates of 2007 a step closer to reality. Funded largely by the Danish government and co-sponsored by The Economist, Copenhagen Consensus has identified the ten greatest problems facing humanity. The items on the list, which range from financial instability to communicable diseases (the complete set appears in the graphic on this page), were chosen in a process that involved focus groups and feedback from experts. In Denmark this May, Copenhagen Consensus will convene nine of the world's top economists--Jagdeesh Bhagwati of Columbia University, Robert Fogel of the University of Chicago, and Vernon Smith of George Mason University, among others--to prioritize solutions to the problems on the list by examining the costs and benefits of each approach. Provided with a wealth of information from the top economic experts in each area, this economist dream team will evaluate several solutions for each challenge and estimate the costs and benefits of all of it. (An example of a solution in the area of communicable diseases is dispensing insecticide-treated mosquito nets, which would reduce malaria infection.) Each economist will arrive at his own figures, and the median of these figures will be the basis of a ranked list. And whatever becomes the No. 1 item on the list will be, according to some of the best analytical minds on the planet, the one thing the world could do to achieve the most for humanity.

Yes, this is ambitious and, to some, preposterously presumptuous, if not outright horrifying. And yet societies and governments implicitly prioritize all the time. Every time we spend a dollar on one project, or pay attention to one example of suffering, somewhere else another good cause goes without. We refuse to do triage because it is difficult and heartbreaking--and the result is that we help fewer people than we could.

In an ideal world, decisions like these wouldn't be necessary. Scientists and governments would be able to achieve everything simultaneously--they would eradicate corruption and improve sanitation, not to mention end conflicts, global warming, and malnutrition, and win the war against communicable diseases. But in a world where resources are limited, it is vitally important to have a rational basis for every dollar spent.

Will Copenhagen Consensus be taken seriously? Yes, it will, partly because Copenhagen Consensus already has the support of a diverse group of intellectuals, writers, politicians, and decision makers, and partly because the quality of information produced will be incredibly high. But the main reason is that it is based upon a very powerful idea: More knowledge can save more lives.

The logic is simple. Consider the kinds of questions such a systematic analysis will answer: Will we do more to ameliorate human suffering by beginning to spend that $50 billion on decent sanitation to half of the world's population, or by dedicating the money to combating corruption in developing nations?

If this kind of triage is so logical, why hasn't anyone done it already? The glib--yet accurate--answer is because it is very, very hard. There are many interested parties. No organization wants its solution to come last, and no country wants its problems to be deferred in favor of another's. And collecting experts with the broad, deep knowledge required is exceedingly difficult. In fact, one accomplishment of Copenhagen Consensus is that nine such illustrious individuals should collaborate on one task.

Next skeptical question: Why have natural scientists--the climatologists, epidemiologists, and so forth who know the most about these problems--not done the prioritization? Scientists are excellent at telling us about problems and possible solutions in their own fields, but are unable to provide us with a way to compare between fields. If you bring together a malaria expert and a climatologist, they will agree that climate and malaria are both big problems, but blood will spill if you ask them to decide which to address first. In essence, experts provide us with a menu of good things to do, but a menu without prices. This is where the economists come in--their entire profession is about dealing with scarcities and setting priorities. The economists will be able to affix prices to the menu, information that is invaluable for governments confronting tough decisions.

By 2007, Copenhagen Consensus will have changed the way we think. As the second Copenhagen Consensus prepares to convene in 2008, rational decision-making will once again be at the forefront of political debate. The organizations that came out on top in the 2004 Copenhagen Consensus will be touting this fact to donors. Organizations that ended up far down the list will face critical questions as to why anyone should fund them first. People will write their legislators and demand that bad initiatives be taken off the table--why commit to a project that costs a lot, yet does relatively little?

By 2007, opposition to the idea of prioritization will have peaked and then abated. The groups--mainly NGOs--that opposed prioritization because "we should do everything" will have realized from experience that, by making our spending more rational, we can achieve more. The prioritization approach will routinely be used by governments to plan health-care spending and to work out the most efficient ways to boost education. Although plenty of well-intentioned people would still rather do everything, many more will have realized that the tough priority decisions that everyone makes every day in their own lives must also be made on a global level.

Of course, the highest-ranked problems and solutions will change over time. But if Copenhagen Consensus succeeds, it will clarify where the world should concentrate its efforts to do the most good for the most people.

BJORN LOMBORG is the author of The Skeptical Environmentalist and heads Copenhagen Consensus (www.copenhagenconsensus.com).