Rafael Nadal and David Ferrer are playing in the French Open final tomorrow. They're currently number 4 and 5 in the world ranking list, but irrespective of the result of tomorrow's game, Ferrer will move up above Nadal in the rankings. That's because tennis world rankings cover the last twelve months, and Nadal's win last year will drop out of the total points, so he can't increase his total score even if he wins, while Ferrer only got to the semi-final last year, so he's guaranteed to increase his total.
Is this a good system? Actually, I think it is pretty good, and any kind of silliness like that is just of academic interest - Nadal will zoom back up to first or second later this year anyway, when he plays in the tournaments he missed through injury in 2012. The really interesting part is that tennis rankings give you a certain number of points in each tournament, depending which round you reach. This I think is less of a good system - if you're a lower-ranking player and you get drawn against the likes of Nadal in the first round, you'll score less points than some other lower-ranking player who gets a lucky draw and gets through to the third or fourth round without playing anyone really good. I'm sure it evens out, but there does seem to be quite a lot of random chance involved.
Or maybe I'm just prejudiced because othello has a cooler system. Your ranking points (there isn't a universally-accepted world ranking, though the one on the French website has gained a lot of support these past few years; the one that British people care about is the British rankings) go up and down depending on the ranking points total of the individual players you win or lose against. Othello doesn't have knockout tournaments, so we couldn't use the tennis-style rankings even if we wanted to, but nothing's stopping tennis from adopting othello-style rankings. Maybe they should.
And othello doesn't claim to have invented that system, I just like to talk in terms of the things I like. Just in case anyone was wondering.
Memory sports, of course, has a different kind of thing altogether. You get a certain amount of points in a competition, and your world ranking score is the highest you've ever achieved in a competition. Even if your best score was donkey's years ago. That's an okay system too, but I'd like to see something based on people's best scores in individual disciplines - perhaps two different ranking lists, in fact - one based on just scores achieved at the world championship, another based on all the disciplines from all the different types of competition. Maybe I'll work these alternatives out and see if there's any way to make my "official world ranking" (another thing about memory competitions is that people freely use the word "official" to describe anything they want) higher than fifth-best in the world!