http://cristblog.drf.com/crist/More Favorites
It began with an innocent inquiry to DRF from someone updating a book, wanting to know if favorites still won roughly a third of the time as they did a decade ago. One very long database search later, it turns out that the ancient rule of thumb that favorites win one-third of all races may need a longer thumb: In 2009, favorites in fact won 36.66 percent of the 55,984 thoroughbred races run in the United States and Canada. That's 20,521 winning favorites, 10 percent (1,860) more than the rule of thumb's 18,661.
Listed below are the 71 tracks that ran 150 or or more races last year, and the number of races and number and percentage of winning favorites. They are not broken down by surface, distance or various other factors that it may be interesting to query as part of an even longer search some other time, simply by where they were run. The data is presented alphabetically by track on the left and then reiterated ranked by highest to lowest percentages of winning favorites on the right.
Of the 71 tracks, 54 had more than 33.33 percent winning favorites while only 17 had less. Favorites won at 39 percent or higher at 18 tracks, and at 40 percent or higher at 10.