Why Are Job Training Programs So Bad?

Ben Casnocha wonders:

For every 14 people laid off in the Great Recession and now rehired, only one has recovered the same or greater salary. To maintain as good or better wages in a competitive economy, you need better skills. The federal government spends $18 billion a year on 47 job training programs run by 9 different agencies. But, according to the Government Accountability Office, "little is known" about the effectiveness of the programs. How the heck do we design job training programs that actually work? How do we measure success? These are vital questions, and while there's plenty of agreement that the topic is important, I haven't seen as much on the nuts and bolts.