If you weren't aware, many places, such as Maine, where I live, set the age of consent at 16
Or lots of places outside of America. In a few European nations, it's actually lower than the 16 here in Blighty.
Looking at this
chart, I'd say the average age in the US is 16. In addition, there are exceptions (lower ages) in some states where the 'victim' and 'perpetrator' are close in age (for example, a 14 year having sex with a 17 year old).