This 4x6 index card has all the financial advice you'll ever need from Harold Pollack

Is the U6 unemployment number the one you should really pay attention to?

Probably....

Here's the breakdown according to Wikipedia.

The Bureau of Labor Statistics also calculates six alternate measures of unemployment, U1 through U6, that measure different aspects of unemployment:^[41]

• U1:^[42] Percentage of labor force unemployed 15 weeks or longer.
• U2: Percentage of labor force who lost jobs or completed temporary work.
• U3: Official unemployment rate per the ILO definition occurs when people are without jobs and they have actively looked for work within the past four weeks.^[43]
• U4: U3 + "discouraged workers", or those who have stopped looking for work because current economic conditions make them believe that no work is available for them.
• U5: U4 + other "marginally attached workers", or "loosely attached workers", or those who "would like" and are able to work, but have not looked for work recently.
• U6: U5 + Part-time workers who want to work full-time, but cannot due to economic reasons (underemployment).

Note: "Marginally attached workers" are added to the total labour force for unemployment rate calculation for U4, U5, and U6. The BLS revised the CPS in 1994 and among the changes the measure representing the official unemployment rate was renamed U3 instead of U5.^[44] In 2013, Representative Hunter proposed that the Bureau of Labor Statistics use the U5 rate instead of the current U3 rate.^[45]

https://en.wikipedia.org/wiki/Unemployment

The Little Book of Economics: How the Economy Works in the Real World