Taken from Wikipedia ( I’ll find better sources for those who are concerned )
Nocturnal emission - Wikipedia
The frequency of nocturnal emissions is highly variable. Some men have experienced large numbers of nocturnal emissions as teenagers, while others have never experienced one. In the United States, 83% of men will experience nocturnal emissions at some time in their life.[2] For males who have experienced nocturnal emissions the mean frequency ranges from 0.36 times per week (about once every three weeks) for single 15-year-old males to 0.18 times per week (about once every five-and-a-half weeks) for 40-year-old single males. For married males the mean ranges from 0.23 times per week (about once per month) for 19-year-old married males to 0.15 times per week (about once every two months) for 50-year-old married males.[3] In some parts of the world nocturnal emissions are more common. For example in Indonesia surveys have shown that 97% of men experience nocturnal emissions by the age of 24.[4]
Some men have the emissions only at a certain age, while others have them throughout their lives following puberty. The frequency that one has nocturnal emissions has not been conclusively linked to frequency of masturbation. Alfred Kinsey found there may be "some correlation between the frequencies of masturbation and the frequencies of nocturnal emissions. In general the males who have the highest frequencies of nocturnal emissions may have somewhat lower rates of masturbation. Some of these males credit the frequent emissions to the fact that they do not masturbate; but it is just as likely that the reverse relationship is true, namely, that they do not masturbate because they have frequent emissions."[5]
One factor that can affect the number of nocturnal emissions men have is whether they take testosterone-based drugs. In a 1998 study by Finkelstein et al, the number of boys reporting nocturnal emissions drastically increased as their testosterone doses were increased, from 17% of subjects with no treatment to 90% of subjects at a high dose.[6]
13% of males experience their first ejaculation as a result of a nocturnal emission.[7] Kinsey found that males experiencing their first ejaculation through a nocturnal emission were older than those experiencing their first ejaculation by means of masturbation. The study indicates that such a first ejaculation resulting from a nocturnal emission was delayed a year or more from what would have been developmentally possible for such males through physical stimulation.[8]