COPENHAGEN – If you had $75 billion to spend over the next four years and your goal was to advance human welfare, especially in the developing world, how could you get the most value for your money?That is the question that I posed to a panel of five top economists, including four Nobel laureates, in the Copenhagen Consensus 2012 project. The panel members were chosen for their expertise in prioritization and their ability to use economic principles to compare policy choices. Over the past year, more than 50 economists prepared research on nearly 40 investment proposals in areas ranging from armed conflicts and natural disasters to hunger, education, and global warming. The teams that drafted each paper identified the costs and benefits of the smartest ways to spend money within their area. In early May, many of them traveled to Denmark to convince the expert panel of the power of their investment proposals.The panel’s findings reveal that, if spent smartly, $75 billion – just a 15% increase in current aid spending – could go a long way to solving many of the world’s challenges.The single most important investment, according to the panel, would step up the fight against malnutrition. New research for the project by John Hoddinott of the International Food Policy Research Institute and Peter Orazem of Iowa State University focuses on an investment of $3 billion annually. This would purchase a bundle of interventions, including micronutrient provision, complementary foods, treatment for worms and diarrheal diseases, and behavior-change programs, all of which could reduce chronic under-nutrition by 36% in developing countries.In total, such an investment would help more than 100 million children to start their lives without stunted growth or malnourishment. And comprehensive research now shows that such interventions would stay with them for life: their bodies and muscles would grow faster, their cognitive abilities would improve, and they would pay more attention in school (and stay there longer). Studies show that, decades down the line, these children would be more productive, make more money, have fewer kids, and begin a virtuous circle of dramatic development.Such opportunities come sharply into focus when you ask some of the world’s best minds to find the biggest bang for the buck. Micronutrient provision is rarely celebrated, but it makes a world of difference.Likewise, just $300 million would prevent 300,000 child deaths if it were used to strengthen the Global Fund’s Affordable Medicines Facility-malaria financing mechanism, which makes combination therapies cheaper for poor countries. Put in economic terms, the benefits are 35 times higher than the costs – even without taking into account that it safeguards our most effective malaria drug from future drug resistance. Later this year, donors will decide whether to renew this facility. The panel’s findings should help to persuade them to do so.For a similar amount, 300 million children could be dewormed in schools. By not sharing their food with intestinal parasites, they, too, would become more alert, stay longer in school, and grow up to be more productive adults – another cause that needs much more public attention.Expanding tuberculosis treatment and childhood immunization coverage are two other health investments that the expert panel endorses. Likewise, a $100 million annual increase in spending to develop a vaccine against HIV/AIDS would generate substantial benefits in the future.As people in the developing world live longer, they are increasingly experiencing chronic disease; indeed, half of all deaths this year will be from chronic diseases in Third World countries. Here, the panel finds that spending just $122 million could achieve complete Hepatitis B vaccine coverage and avert about 150,000 annual deaths from the disease. Getting low-cost drugs for acute heart attacks to developing countries would cost just $200 million, and prevent 300,000 deaths.The expert panel’s findings point to a compelling need to invest roughly $2 billion annually in research and development to increase agricultural output. Not only would this reduce hunger by increasing food production and lowering food prices; it would also protect biodiversity, because higher crop productivity would mean less deforestation. That, in turn, would help in the fight against climate change, because forests store carbon.When it comes to climate change, the experts recommend spending a small amount – roughly $1 billion – to investigate the feasibility of cooling the planet through geo-engineering options. This would allow us to understand better the technology’s risks, costs, and benefits. Moreover, the research could potentially give us low-cost, effective insurance against global warming.Another priority for investment is the establishment of effective early-warning systems for natural disasters in developing countries. For less than $1 billion a year, this would alleviate both direct and long-term economic damage, possibly securing some $35 billion in benefits.The $75 billion budget chosen for the Copenhagen Consensus project is large enough to make a real difference, but small enough that we must choose – as in the real world – the projects that can achieve the most good. The expert panel’s list shows us that there are many smart solutions waiting to be implemented.Bjørn Lomborg is an adjunct professor at the Copenhagen Business School, where he founded and directs its Copenhagen Consensus Center