Testable theories
Jan Tinbergen - the first person to be awarded the Nobel Prize in Economics - became known for his 'Tinbergen Norm'. This states that if the difference between the lowest and highest income in a company exceeds a rate of 1:5, that will not help the company and may indeed be counterproductive.
In 2000, the ratio of average-CEO-to-average-worker was 525 to 1.
Disclaimer: I could not find an original source for the Tinbergen Norm. I'll have another go at it and report back soon.
