I bet not more than I can imagine... but I’ve been involved in the issue for some time. I’m always glad and impressed by people and groups who are actually willing to help.
There actually are homes for most of the ones going to slaughter. As the market in recent years has shifted from pet food (they won’t buy horse any more) to human consumption, the kill buyers are looking for younger, healthy horses to slaughter. They are benefiting now, not from an actual glut of unusable horses, but a poor economy that has dropped the sales prices for even good sound horses down into the affordable range.
On edit... human consumption overseas of course... not here.
And even overseas, not for long.