The official definition of U-6 is:
Total unemployed, plus all marginally attached workers, plus total employed part time for economic reasons, as a percent of the civilian labor force plus all marginally attached workers.
Marginally attached workers are persons who currently are neither working nor looking for work but indicate that they want and are available for a job and have looked for work sometime in the recent past. Discouraged workers, a subset of the marginally attached, have given a job-market related reason for not currently looking for a job. Persons employed part time for economic reasons are those who want and are available for full-time work but have had to settle for a part-time schedule.
Yada yada yada.
In essence, U-6 covers everyone who's either unemployed, whether they receive unemployment benefits or not, or might be working a part-time job but who really want to be working full-time (i.e., they're underemployed).
On to the statistics then. In October, the "official," U-3 unemployment rate was 6.5%. This is the highest unemployment rate we've seen since March 1994. However, the U-6 unemployment rate in October was 11.8%. This is the fourth month in a row that U-6 has been over 10%, with the lowest rate this year having been in February, at 8.9%. The last time U-6 was this high was in January 1994, when it was 11.8%. (Ironically, this is also the very first month U-6 was published.)
As most economists are presuming today, the country is almost certainly in a recession at this time (even though it hasn't been officially announced yet). How do these unemployment rates, then, compare against the last three recessions? U-6, being a rather limited series of data, only covers one time period when unemployment was almost as bad as it is today. In June 2003, U-3 peaked at 6.3%, while U-6 peaked in September, at 10.4%; the largest spread between the two unemployment rates that year was 4.3%.
The next earliest spike in unemployment rates happened in June 1992, when U-3 reached 7.8%. However, there wasn't any U-6 rate at that time, so we can only guess what it might have been. Doing a little spreadsheet analysis, my own guess is that the spread between U-3 and U-6 at the time was about 5.3%; add that to the 7.8% and the hypothetical U-6 unemployment rate may have been about 13.1%. The worst of the three recessions, though, was that of the early 80s. U-3 peaked in November and December 1982 at 10.8%; this is the only time U-3 has ever peaked above 10% since 1948, when the current series of unemployment rate data starts. Assuming that the spread between U-3 and the hypothetical U-6 was still around 5% at that time (and I think it may have actually been larger), total unemployment and underemployment probably would have been around 16% in late 1982.
So. Unemployment is bad now. It's slightly worse than it was six years ago, but it's also not as bad as it was back in the early 90s or the early 80s, which was much, much worse. Consider that your positive thought for the day. ;)