The current economic recovery in the United States has featured an almost continuous decline in the labor force participation rate. While this decline is much discussed as a sign the economy may not be recovering, there has been a downward trend since the year 2000. So, the question is whether this decline has recently accelerated or not. Or, in other words, is it mostly cyclical or mostly structural? FRED offers plenty of more-detailed series to analyze this question. St. Louis Fed President James Bullard recently wrote a Review article about the labor force participation.
How this graph was created: Simply search on FRED for the civilian labor force participation rate (CIVPART).
Suggested by Christian Zimmermann.