Steve McConnell in Making Software:
This degree of variation (in productivity and quality) isn't unique to software. A study by norm Augustine found that in a variety of professions -- writing, football, invention, police work, and other occupations -- the top 20% of the people produced about 50% of the output, whether the output is touchdowns, patents, solved cases or software [Augustine 1979]. When you think about it, this just makes sense. We've all known people who are exceptional students, exceptional athletes, exceptional artists, exceptional parents. These differences are just part of the human experience, and why would we expect software development to be any different?
How many millions of dollars has the Gates Foundation spent in an effort to get everyone to mis-interpret this phenomenon in respect to teaching?