Contrary to popular belief the age of consent is rarely 18, statistically speaking, except for people in a position of authority. (teachers, step moms and stepdads, babysitters etc). There is a difference between taboo law ("nothing under 18") and real law ("the age of consent is 16 in connecticut"). The reason they differ is because lawmakers are forced to do something that society isnt: be honest.
Also contrary to popular belief you do NOT have to be an adult to be arrested for statutory rape (sex with someone under the legal age).
The age of consent varies from state to state country to country. It's wise to consult an attorney if you are dating a minor and ask about local laws.
*Homosexuality is usually higher.