I've seen several studies that attempted to quantify this, with varying estimates.
Consistently, across all ages, males wet the bed at approximately twice the rate of females.
I've seen studies that put the rate of adult bedwetting between 0.5%, and 2.7%. A major inconsistency is that these studies don't always define bedwetting the same way, or sometimes at all. Some studies classify a person as a bedwetter if they wet more than 6 times in 6 months, others more than twice a month, others simply ask if the person is a bedwetter (and either the respondent or doctor is left to make a judgement about how often qualifies). If you survey a group of people and ask, "are you a bedwetter", you get a much lower response than if you ask, "in the last month, have you experienced any involuntary loss of urine while sleeping".
The most realistic result I've seen from a study put the number around 1.5%, 1% of women, and 2% of men.
