Employment numbers would be a good start..
...aside from being a spectator sport, it provides full or part time jobs for approx. 250,000 people and 300,000 have a direct interest as owners or members of syndicates...then you have the indirect industries as a result of horse racing....such as farriers, grain and horse feed suppliers, equipment (saddles, jockey clothing, floats etc)..
...also contributes 2.1 billion to the victorian economy per year.....and that's just victoria.
Jesus Christ
I've spent much of my adult life working for unions, and even I think that "employment numbers" is a ridiculous way to gauge the "size" of a sport. If you're doing that you need to do it for all sports, not just the one you're advocating for. So you're adding up every person who gets a few bucks to coach a soccer team, to referee a game, to play, to work with the association; everyone who sells a jersey at rebel sport, everyone who has worked at a stadium in the last year, everyone who works at a factory who makes every club teams jersey, even the people that work at the company that sponsors teams and leagues (which, for example, is everyone who works at Westfield.)
It is beyond ridiculous to try and measure a sports size in that way, cos there's no way that it's truly measurable, and there's no way to compare apples with apples.
Also, when it comes to contribution to the economy, there's also no real way to measure this, because everything that is gambled gets measured at least twice (when it comes in and when it goes out). And given most people end up wagering any winnings multiple times, it's the same money that's getting counted multiple times.
As I said yesterday - we already have a radio station dedicated to racing, and no one listens to it. No one needs SEN to become a second.