Creepy OP.
Western teenagers generally start having sex on average when they are 16-16.5 years old, this is fairly stable across various countries. So 16 means almost half of teenagers start having sex when they are underage. This is the main reason we have the age of consent at 15 in my country - it is simply more realistic and does not criminalize so many relationships. Still, 15 is a bit young to have sex with an adult (you mature fast in that age, so a year means a real difference). So if you are going to have one age of consent for all I think 16 is the most reasonale, but can live with 15.
An alternative is the 10 year+ rule for under 18s (you can have legal sex with minors above, say 14, if you are less than 10 years older than them), but that is artificial and guys in their 20s can prey on teenagers as well as older men (and older teens on young teens), so it is generally not a sensible idea.
That a terrible idea. A lot of men are celibate in their teen years and missed out. Teenage girls can stay virgins but if they are sexually active it doesn't matter if it's with a guy their own age or ten years older. Guys who get laid young tend to be losers while men who do great things take longer to develope themselves but soften get stuck with older woman and miss out on those years. In the past teenage girls would marry as virgins to older men.
My love life sucked in high school but I can say at the age of 27 that 18 years old is young enough for me pal. I don't want a date who looks like a freaking kid. I don't like jail that much.