First you'd really have to qualify some things. How do categorize imported horses? What if they showed FEI over there and now GP here? Also, by Europe, do you mean Germany and the Netherlands? What about Spain, France, Sweden... Also, in Germany, you have to qualify all the way to GP, and you qualify against the open riders (no amateur classes, in my understanding). It is very hard to move up the ladder to GP because the competition is soooooooo rigorous and there are limited slots in the shows. So, there may be horses who are GP quality who just don't make it to GP over there because the owner doesn't pay a top rider to bring it to GP.
North of the Frozen Tundra, but I can see it from my house.
Maybe the question could be how many of the horses currently showing in recognised dressage shows are showing at Grand Prix? I would be interested in a breakdown of all the levels. Riders too; how many are showing at each level.
This is an interesting question. I think that the real issue is- How many people out there are willing to pay the money for a GP horse, AND can actually ride/show one? Very few. Therefore, since the market is so limited, there is much less impotice for professionals to try and produce, or import, these horses. They have to be able to sell them for what they have in them, afterall.
How many cars does Toyota sell in a year? Aston Martin?
Most people top out at about second level. And, most people want to be able to ride their own horses- that's why they buy them.
There aren't that many George Williams, or Debbie McDonalds, out there with big time sponsors for their horses, who give them the time to bring them along, and money to compete and live, and are not looking to have a complete return on their investment.
In my area, we have one trainer I can think of who has produced a bunch of GP horses. Everything she buys, she brings along, and teaches all the tricks to before she offers them for sale. She can afford to wait on them, and she gets a nice return on her money- but she is rather unusual, and has a ready market for the few she offers for sale.
I can say that in Europe this percentage is much lower, not even 1%.
This has to do with the fact that we have to climb up the ladder, getting scoring points in every class, from B-L-L1-M-M1,Z,Z1,ZZL,ZZZ, FEI to get to the top.
And also without amateur classes (at least in Germany), all riders have to compete against the National A and B list at FEI, which really puts a damper on moving up. One must pay alot and find a top rider/trainer to get a horse to the very top in Germany. Also, alot of horses retire to breeding after the young horse championships or are exported...moreso than in the US.
i am not sure if the OP was looking only for horses that compete? but i would imagine that there are more that dont compete.... as an example: i know of 7 GP horses that are not competing - just within a few miles of me.... i am sure there are many more....
i think the moment you add competiton into it the percentage goes way down.