U6 not the real unemployment rate

Cato says U6 is not the "real" unemployment rate.

I think U6 is attractive to permabears and "progressives" because it fits their pessimistic view of the world.

I don't think it matters whether you use U1, U2, U3, U4, U5, or U6, because they move in lock step with each other. Just pick one and stick with it. U3 is the official unemployment rate and is most widely reported.

What matters is not the unemployment rate per se, but the unemployment rate compared to the natural rate of unemployment (i.e. NAIRU, "full employment"). For U3, the natural rate of unemployment is about 5%, so when it's above that we know things are bad. If U3 falls much below 5%, inflation cometh. I don't know what the natural rate of unemployment is for U6, and I bet most people who insist on using it don't know either.