They do not have a good source of the total number of licenses or ownership transfer information. A single total number for all licensed craft above 9.9 horsepower is about all they have. Where does the owner buy it or use it, only get data on where it was registered. Many are trailered a long ways. Data is based on state lines and only on where they live.
Some states capture primary use data.
Florida dealers have people who winter there who may buy a boat somewhere else. There are only about 5 U.S. companies involved in making marine engines or PWCs, but there are over 350 boat companies. Boat data is much more difficult to collect and aggregate. I asked this question. They could not realize why they would want to do that.