In answer to the question: Why is it that there is an even gender balance among ringers in the early stages of ringing, but the gender
distribution changes at more “advanced levels”?  As a gay man, I have often noticed the time that can be taken up raising families in (women's) 20s, 30s and 40s and the impact that can have on their ringing careers.  

It is difficult to get data to back this up, but there is strong anecdotal evidence that the proportion of gay male ringers seems to be higher in ringing than in society in general. It seems the average 12-bell contest final band has two or three female ringers, and two or three gay male ringers.  Sampling some prolific peal ringers statistics for ringers they have rung the most twelve bell peals with presents a similar pattern.  The UK population is represented 51% by women, and 1.25% gay males.

Gay men are generally not spending time raising families and have more time to put into ringing.  Perhaps this indicates, and potentially skews, the reason why women are less well represented at higher levels in ringing?