I would like to see the results too, but I doubt they exist (beyond the obvious: if you want to have 50% male and 50% female employees, make an internal rule to hire 50% men and 50% women).

Beyond evidence... my heuristic would be to start the organization with gender diversity. It should be easier to find e.g. 3 men and 3 women to start an organization, then to have an organization of 100 men and later think about how to make it more friendly for women.

EDIT: Also, you should not have a bottom line already written that having 50:50 ratio is improving. People do have different preferences. A ratio other than 50:50 might reflect the true level of interest in the base population.