[richmarr]

> Are there?

Yes.

> Diversity defined how?

Depends on the study. Usually gender or race.

> Repeatable experiments or statistical analysis of groups of companies?

Depends on the study. See my other comments in this thread.

> It could be studied experimentally and so I am sure it has been.

It has been. See the study into racially diverse juries making more accurate judgements.

> The studies using statistical analysis to compare across companies are always weak and should be taken with a grain of salt.

Everything sould be taken with salt because salt is awesome.