There have been many threads on this issue. In general people tend to spend a fair proportion of their lives as both genders (and a few of the 'in-between' gender state). Some tend to favour one gender over the other, say 80/20. Others are 60/40, 50/50, 70/30,whatever. It varies There aren't really any reliable 'stats' on this, just anecdotes and obviously most people don't remember all their lives, usually just a few, so it's hard to say for sure. Personally I think it's got a lot to do with what body is available at the time which tends to be a bit random. I don't think the soul really cares what gender the body is, but obviously the life experience will be different for different genders, depending on the culture one is born into.
A search on 'gender' will bring up threads about this.