You've probably seen some alarming charts about the labor force participation rate lately. Here's a chart that I find less alarming, breaking the numbers out by gender.
The slow steady decline of male labor force participation is a fascinating issue. I wish we understood it better. But it's been happening literally as long as the statistical series has existed. That's part of what makes it so fascinating. It appears to be impervious to the macroecononomic cycle or the changing fads of public policy. For comparison's sake, in Germany where the labor market is much healthier right now than in the USA the male workforce participation rate has stabilized but at a much lower level than in the United States. And that's in an economy more geared toward manly manufacturing jobs.