The U.S. unemployment rate is at an 18-year low,

The unemployment rate is basically the difference between the labor force participation rate and the civilian employment to population ratio.

And the labor force participation rate is close to a 40-year low and the civilian employment to population ratio is only at levels last seen in 2009,

One could attribute the labor force participation rate decline on fewer older people participating in the labor force (by retiring early) but that isn’t the case. Increasingly, more people in the over 55s and over 65s age brackets are participating in the labor force,

It is mainly that fewer people in working age group are participating in the labor force,

Related: This is what has happened to the unemployment rate in the US four to eight months before every recession since the 1940s and why it matters now (Read here)