How does rankings work?

I know how the PWT works but what about the other tournaments. I remember reading once about the Pro Ranking list which took the last 13 WWA professional tournaments inclusive of the PWT. But now you have these world events (World Cup and World Series) which only one is WWA and neither have all the riders. So how do tournamnets like Nationals and Wakestock rank riders for seeding?

I know golf and tennis use the last of so many tournament and the points start diminishing as itme goes on. So if you use the last 25 events the 25th one or the one which took place the furthest time ago, would have the least value. For instance, this years tournaments would all be worth 100% but last years would be less, say 90% for the last tournament and 75% for the first. So if you won both of those valued at 100 points the first one would be worth 75 points (.75 x 100) and the last would be worth 90 (.9x100).