I've had a lot to say on the difference between agile development methods and their predecessors is a focus on effectiveness rather than cost accounting style efficiency. Others in the community have picked up on this theme too and the relationship of efficiency and cost accounting back to Frederick Taylor and time'n'motion studies from the turn of the 20th Century have been drawn. Taylorism was about specialization and efficiency of specialists - local optimum hoping for a global optima - whilst modern lean/agile thinking is about effectiveness of adaptable generalists and systems thinking with alignment around a global optimum.

Peter Drucker has had quite a bit to say about effectiveness and knowledge workers. Most of what follows is taken from "The Effective Executive" from 1966 - note a clear 3 years before The Psychology of Computer Programming by Gerald Weinberg. In the mid-Sixties, software engineering had something to learn from general management science but at the time the link had never been made.

"To be effective is the job of the knowledge worker."

"people of high effectiveness are conspicuous by their absence in knowledge jobs. High intelligence is common enough amongst knowledge workers. Imagination is far from rare. The level of knowledge tends to be high. But there seems to be little correlation between a man's effectiveness and his intelligence, his imagination, or his knowledge. Brilliant men are often strikingly ineffectual; they fail to realize that the brilliant insight is not by itself achievement."

"Intelligence, imagination, and knowledge are essential resources, but only effectiveness converts them into results."

He then separates the Taylor era from the modern knowledge worker era so effectively with this definition...

"For manual work, we need only efficiency, that is, the ability to do things right rather than the ability to get the rights things done."

Efficiency = Do Things Right
Effectiveness = Do The Right Things

"Increasing effectiveness may well be the only area where we can hope significantly to raise the level of the knowledge worker's performance, achievement, and satisfaction."

"One of the weaknesses of young, highly educated people today ... is that they are satisfied to be versed in one narrow specialty and affect contempt for the other areas."

Drucker comments that finding effective people is difficult and makes an observation that today we would summarize as  - There is No 'Effective' Myers-Briggs Type.

"there is no 'effective personality.'"

He goes on to observe that effectiveness is not achieved from principles but from successful execution of practices. If we are to learn from Drucker, it is that we cannot merely talk about agile development in abstract principles - even though this is the simplest way to gain consensus in the community - in order to show effectiveness we must articulate practices which deliver productivity.

"Effectiveness is a habit; that is, a complex of practices. And practices can be learned."

Hence, Drucker leaves us with hope - the hope that all we have to do is to teach, coach, mentor and instill the correct set of practices in the individual knowledge worker and effectiveness will follow. What is largely lacking in the teaching of software engineering as a profession is just that - the set of practices which lead to effectiveness. If we can fix that both at the academic level and within industry itself then we can start to deliver the value that shareholders deserve from their expensive knowledge workers.