How prevalent is anal among straight couples?

Did the whole naughty boy things in boy scouts during the summer camp, but it was only humping each other's booty. The first time I actually slipped my penis inside a booty was with a girl who I met the summer before I started the ninth grade. She was the one who told me how to use Vaseline and she said she wanted me to do her in the butt From that point on I was hooked on the the whole butt sex thing. After that I would eventually ask every sexual partner I have been with to let me do them up the ass! Of course 7 out of 10 would say no, but I would always ask.