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?