In 2015, the UN General Assembly adopted the Sustainable Development Goals (SDG), which identify 169 targets for the world to hit by 2030. Lomborg’s think tank, the Copenhagen Consensus Center, thought that was too many, so it brought together a group of economists to conduct a cost-benefit analysis of each one (except for those that were too qualitative to evaluate). This useful book is the result, covering topics ranging from air pollution to water and sanitation. For each SDG, the contributors assess how much the world will have to spend and what it will get for the money. Prioritizing is important, since governments and donors will not be able to spend nearly enough to meet all the targets. The contributors conclude that the highest return would come from completing the stalled Doha Round of trade negotiations, which they estimate would boost the global economy by over $2,000 for each $1 spent. On the other hand, they project that trying to meet some other targets, such as guaranteeing employment for everyone, would return less than it would cost. The book concludes that apart from trade liberalization, the highest payoffs would come from immunizing vulnerable populations, reducing malnutrition among young children, and fighting tuberculosis.