While formal apprenticeship programs have declined, learning by doing has not. For example, how much of what you do now was learned on the job compared to in school? Yet, schools get most of the credit for knowledge gained.

Most people still learn their jobs by training under experienced practitioners, from plumbers to particle physicists. This means that our mode of learning hasn't changed in modern times, but we often don't recognise it.

Teaching students in a classroom is cheaper than training them on the job, which can be very costly. 

However, apprenticeship suffers from credible commitment - the master wants cheap labour, and the apprentice wants to learn. But if the apprentice learns too quickly, he ca...