Hey there. Finding accurate stats is difficult to find. Since none of the companies (except for Johnson Outdoors) are publically traded, there is nothing forcing them to release their finicial information.
The National Marine Manufacturers Association prints a recreational stats for each year that coves a huge amount of info.
The only problem is that it costs $775 to grab the entire book (it's huge). They publish a free abstract that has a sample of the number of boats sold. It might help get you started.
www.nmma.org/facts/boatingstats/2006/
When I checked now, it was giving me some problems downloading but it has worked in the past.
Also, you might want to try the Trade Association of Paddlesports, They might be able to give you some pointers. You can reach them at
www.gopaddle.org.
I hope that this can get you started.
David J.
www.paddlinginstructor.com