Shown below are the stats for how favourites ran on different types of ground. You'll notice that at the extremes of ground, Firm & Heavy, they have better SR's than the norm. This goes against what is normally thought and that Favs win much less in extreme going.

So why is this, it's not due to the lower sample base, their are enough qualifiers for pretty accurate stats. The reason is based on the number of non-runners you get with extreme ground making it easier for Favs to win. Keep that in mind next time it rains heavily or the Sun shines for days.

Official GoingRanWonWin SRP/L BFP/L SPLay P/L BFWin & Plc SR
Firm56022840.7134.7812.06-70.6965.54
Good11344368032.44-567.18-1026.41-189.5460.56
Good To Firm9129317834.81-111.58-480-493.362.67
Good To Soft5698190033.35-171.84-402.9-208.9161.32
Heavy220979535.99-100.6-175.95-39.2263.88
Slow532037.74-1.53-3.23-1.7862.26
Soft5700195234.25-309.14-525.6-59.2561.19
Standard10020337333.66-277.96-794.58-389.662.76