Horse racing as an ML ranking problem: 1.18M runners, walk-forward validation and a very strong market baseline [D]

Hi 👋 long time lurker It’s been a few years since the last post about Horse Racing within this sub. A few years ago I was reading a popular science book and came across the story Bill Benter and the statistical models his team developed for Hong Kong racing. What stayed with me wasn’t simply the idea of using a model to gamble. Horse racing seemed like an unusually difficult applied ML problem: variable-sized fields, one winner per race, highly correlated competitors, missing and changing data, human decision-making, non-stationarity and an extremely efficient market baseline. What’s more, Hon