It’s hardly news that people spend money on stupid things. Thankfully, Porter is interested in more than factoids. Most of his attention is devoted to teasing out the rationale underlying the “cold accounting” that determines the value of things people think are priceless, like human life and national security. What he relates has unmistakable urgency. How much should we spend today to address environmental problems that may be more cheaply tackled by future generations, especially given the number of development projects that clamor for financing now? Should we even attempt to protect against risks that would be more costly to prevent than the damage they would cause?

Most of Porter’s evidence is culled from sources like the National Bureau of Economic Research and The Journal of Economic Perspectives — outlets that routinely publish fascinating research cloaked in jargon. His main feat lies in scouring, translating and synthesizing the latest findings of social science into something that the curious layperson would actually enjoy reading. If anything, he is a dollop too diligent: every so often an observation comes off as banal, while other insights contain a waft of the dubious. (Even if the Second Vatican Council did cost the church some believers because it attenuated the rigors of faith, the decline of Roman Catholicism seems much more complicated.)

At a time of seemingly proliferating risks, though, Porter’s searching book is a welcome reminder of the necessity of prudent decision making. “The truth is,” he writes, “we can’t afford it all.”