The Washington Post Style Invitational compiles statistics on all the winners. Actually, it's not official but is done voluntarily by one of the people who has entered for the last twenty years. You can look up literally thousands of people who have entered and find out how they did.
Here. They also have yearly statistics and award titles. I was "Loser of the Year" and "Rookie of the Year" a few years back, though overall I am not near the top of the standings with my 204 inks (compared with the champion, Chris Doyle, who has over 2000 inks and back in the days of the New York magazine competition had a similarly ridiculous record of success).
I've never approached the British contests the same way, however. I just enter when I like the prompt the contest provides. Over the last decade or so, I think I've won around 25 times, placing me way outside the top ten.