Think Like a Freak

by Steven D. Levitt

Incentives are the cornerstone of modern life. And understanding them—or, often, deciphering them—is the key to understanding a problem, and how it might be solved. Knowing what to measure, and how to measure it, can make a complicated world less so. There is nothing like the sheer power of numbers to scrub away layers of confusion and contradiction, especially with emotional, hot-button topics. The conventional wisdom is often wrong. And a blithe acceptance of it can lead to sloppy, wasteful, or even dangerous outcomes. Correlation does not equal causality. When two things travel together, it is tempting to assume that one causes the other. Married people, for instance, are demonstrably happier than single people; does this mean that marriage causes happiness? Not necessarily. The data suggest that happy people are more likely to get married in the first place. As one researcher memorably put it, “If you’re grumpy, who the hell wants to marry you?”