In the early 1990s crime rates in the U.S., which had been climbing steadily for decades, began to drop. Then they began to drop much faster. Today, in many parts of the country they’re at historic lows. That shift has had profound effects on everything from U.S. politics—even law-and-order conservatives these days are proposing that we reexamine our incarceration policy—to its geography, as people have flocked to cities such as New York and San Francisco that were once seen as blight-ridden, violent, and anarchic.
Since then, social scientists, politicians, police officials, and activists have been disputing what, exactly, turned what had seemed to be an inexorable rise into a steady fall. The explanations range from the waning of the crack epidemic to innovative policing tactics to Roe v. Wade (PDF). Monday’s ruling by a federal judge that the New York Police Department’s stop-and-frisk program is unconstitutional is one more salvo in the back-and-forth over what we should credit with reducing crime, and it’s certain not to be the last.
It came a week after another piece of news: Obesity rates among American children, after stubbornly rising for decades, have started to decline. According to the Centers for Disease Control and Prevention, what’s most striking and most encouraging about the drop is that it seems to extend to poor and minority children, who have the highest rates of obesity and attendant health problems like diabetes. It does not appear to be a fluke, either—the overall growth in obesity rates had been slowing lately, and certain cities had already reported modest drops.
What’s the cause of the decline? There, again, is the rub. Amid the pronouncements of cautious optimism there’s already an argument over what to credit. One theory is that it’s due to an increase in rates of breast-feeding. Some doctors assert that the practice, by letting babies decide when they’re full rather than leaving it up to the parents, prevents children from growing up into overeaters. Others point to healthier meals in schools, or a decline in the amount of sugary drinks kids consume. A few talk about Michelle Obama’s Let’s Move!, a national initiative to disseminate health information to parents and encourage kids to be more active. Still others suggest that what’s happening has little to do with government interventions such as the First Lady’s.
If the crime conversation is any indication, the obesity debate is likely to continue for a long time. There may never be consensus over the cause. (That’s setting aside the argument over how bad being overweight actually is for you.) It can be hugely frustrating that, even after the fact, we can’t agree on what causes substantial changes in human behavior—changes that, as individuals and as a nation, we’re spending untold effort and money to combat. Human beings, it turns out, are complicated. At the least it should give us a healthy dose of humility.