GREAT but the biggest North American Tiger regatta in 08 was the NA's with 12 boats and 35 or so Class Members. The market is speaking pretty clearly.... OD is not winning the day in the USA.
(Source Nahca standings)
Congratulations, you found a limited piece of data to support the conclusion you wanted to draw...
One design is second to WHAT, exactly?
The F18 situation is the US is somewhat unique. Tiger sailors, given the chance to do a Tiger NAs or a F18 NAs seem to be going to the larger event (this has been discussed at length here).
That in NO WAY means ALL OD cat sailing is slipping to open classes. Hobie 16s and A-Cats, at a minimum, have larger NAs than any "open" class events.
Further, at points regattas, H16s, A-Cats and Tigers tend to have larger classes than any open fleets.
Mike