I recently listened to a podcast that repeated something I've read/heard before. Sometime between the 70s and now, the way "unemployment" is calculated changed dramatically. According these sources, if we calculated unemployment like we did in the 1930s, we'd have unemployment levels in the mid-20%s the last few years.

I wish I had time to research this and find the sources, but since I've read/heard it multiple times, I think it is worth mentioning.