Is income equality in companies a key to success?

In the talk by Richard Wilkinson he speaks about the correlation that was found between (in)equality in countries and their performance in healthcare etc. Bottom line: in the developed world countries with more equality have a longer life expectancy compared the more unequal countries. The inequality metric is a good indicator for many more “good” things. Correlation is of course not causation, but he also mentions some possible reasons why it could be causation.

Now I wonder if the same thing holds true for companies.  How would you handle such research? First you need to find a metric to calculate the (in)equality in a company. One possibility is to calculate the best paid employees salary compared to the lowest paid employee. E.g. the best paid employee earns 40 times the amount the worst paid employee gets. Maybe this metric is too limited as it only compares the extremes. Furthermore you need to determine the success of the company ideally with some metrics. Profit is off-course one but I think it shouldn’t be the only one.

Searching for some answers to the question I found an article saying that the CEO of a company should earn about 20 times the salary of the lowest paid worker. I think CEO is probably too limited as well. Does somebody know research that hints towards correlation between equality and company successes or maybe the opposite?