From Charts 'May to Aug' (no Jan-Apr) but not all dates, just a sampling.
Code:
Track Races Wins Win% ROI on betting the Fave
HAW 385 183 48% 0.912
HOP 500 247 49% 0.994 ...Whaaaat?
NFLD 482 231 48% 0.810
MEA 299 137 46% 0.914
M 237 91 38% 0.748
YR 62 33 53% 0.934
SCD 453 205 45% 0.849
Looks like those Hoosier guys hate betting the Favorites
USTA has HOP at 624 Starts, 48% Winning Favorites