The Female Lead Relationship website has some poll results for women practicing male chastity: http://aboutflr.com/polls/Poll-Results-Experience-of-women-practicing-in-male-chastity.html Of course responses to the poll will mainly be from flr women so the results will reflect this. Lots of interesting percentages, including: 13% of males are permanently denied 27% do not have penetrative sex Not scientific, no total numbers of respondents given, etc etc... but still maybe gives some sort of overall picture. [Also: http://aboutflr.com/polls/Poll-Results-Experience-of-men-practicing-in-male-chastity.html]
That site doesn't seem to get a lot of traffic these days but I'd bet the numbers would still be close