1. In the 1981-82 recession, unemployment peaked at 10.8 percent in November and December of 1982. Starting from December, it took 75 months (six-and-one-quarter years) for the unemployment rate to reach 5 percent (its lowest point before beginning to increase again). Thus, unemployment moved by (10.8-5)/75 = .077 percent per month.
2. In the 1990-91 recession, unemployment peaked at 7.8 percent in June of 1992 (unemployment peaked after the recession ended). It hit 5.1 percent in August 1996, 50 months later. After that, it hovered slightly above 5 percent before reaching 5.1 percent in April of 1997 and then 4.9 percent in May of 1997. Call it 50 months to be conservative in terms of the recovery time. Note also that unemployment hit 4.0 percent in December 1999, 90 months after the peak (seven-and-a-half years).
What is the rate of decline? To get to 5.1 percent, the unemployment rate moved (7.8-5.1)/50 = .054 percent per month. To get to 4 percent, the unemployment rate moved (7.8-4)/90 = .042 percent per month.
3. In the 2001 recession, the unemployment rate peaked at 6.3 percent in June of 2003. It reached 5 percent in July of 2005, 25 months later, and it reached 4.5 percent in September 2006, 39 months later. The associated rates of decline are (6.3-5)/25 = .052 percent per month, and (6.3-4.5)/39 = .046 percent per month.
Using this figure, and starting from an unemployment rate of 10 percent -- the rate that exists today -- how long would it take for the unemployment rate to get to 5 percent?
Answer: (10-5)/.061 = 81.8 months, or almost 7 years. (Getting to 6 percent would take 65.5 months, or just short of five-and-a-half years.)
However, there's an important qualification. The time can be shortened with effective policy. Since seven years is far, far too long to wait to return to something like full employment, and since we have the means to do something about it, we should move quickly to give labor markets the boost that they need.