There are now 8.8 million workers receiving disability payments from Social Security. I find this number haunting…Thirty years ago, there was a 40-to-1 ratio between the total labor force and those workers receiving Social Security disability payments. Today that ratio is less than 18-to-1…

The steady rise in disability claims presents something of a puzzle. Medicine has improved substantially. Far fewer of us labor in dangerous industrial jobs like the ones that originally motivated disability insurance. The rate of deaths due to injuries has plummeted. Behavior that can cause disability, such as alcohol use and smoking, has declined substantially. American age-adjusted mortalityrates are far lower than in the past…

Duggan and Imberman argue that changes in the award formulas for recipients have made disability substantially more generous for poorer workers. For example, a male worker who is 30 to 39 and in the bottom 25th percentile of earnings distribution could expect disability insurance to pay 41 percent of his previous earnings in 1984 and 49 percent of his previous earnings in 2002.

More from Ed Glaeser.