Used to be the males outnumbered the females at birth but because of higher mortality (in infancy, due to dumb accidents) that they were about the same in number during the teens.
After that they die off at a faster pace, at least after obstetrics learned a few tricks to keep women from dying in childbirth.
1950 was the first U.S. census in which women outnumbered men, due to modern obstetrical practices.
And don't forget wars and homicides, both primarily male endeavors.