I actually do vaguely remember two studies which, if memory serves, did back this up. One of them was attempting to establish a correlation between the frequency + 'strength'(?) of these experiences and the ability to have or frequency of having female orgasms - as an apparent follow-up to an earlier study that had established certain "impressive" statistical numbers for the latter.

If I interpreted the numbers correctly, it would imply that it's usually on the order of 30% to 50% (depending on geographical location as correlated to social customs and culture).

I note that the above is probably not a very accurate picture of reality, since it's all from memory and I'm most likely applying all kinds of biases and heuristics to it subconsciously before accessing said memories.