I assume one reason that only 25% are professors while 50% occupy other positions is simply attrition - the rate at which women have caught up in almost every field of study - medicine, law, science has been nothing short of remarkable compared to less than a generation ago.  but those already in those positions such as professors are going to have to die off and be replaced.  Equilibrium is taking shape - but it doesn't happen instantly - unless of course one wants to unjustly fire large numbers of men and fill those positions with women?