Trends in the Transitory Variance of Male Earnings: Methods and Evidence.

We estimate the trend in the transitory variance of male earnings in the U.S. using the Michigan Panel Study of Income Dynamics from 1970 to 2004. Using an error components model and simpler but only approximate methods, we find that the transitory variance started to increase in the early 1970s, continued to increase through the mid-1980s, and then remained at this new higher level through the 1990s and beyond. Thus the increase mostly occurred about thirty years ago. Its increase accounts for between 31 and 49 percent of the total rise in cross-sectional variance, depending on the time period.