There are still regattas in New England, they aren't what they used to be but there are definitely still regattas.

I wish US Sailing would take a real survey and come up with a list like this.
A couple problems I see with the list are that the Laser class has a North Americans and a Nationals... both were capped, they chose the one with less boats, NA's.
We had 130 boats at V15 Nat'ls but there wasn't a single race all weekend because of no wind, it was rescheduled and only 77 boats showed up. Had they used the original it would have put the V15 over the Hobie 16.
Obviously we all know there are more boats than who competes at NAs and each year big differences are seen depending on what region the event was held.
Given that, it is pretty cool the the 16s have such a dedicated class that are willing to travel and maybe if other classes would do that this survey would be more accurate.