Greetings ....
With regards to the (click-on »»)
PGA Tour's Priority Rankings (aka Exemption Categories) List ...
If you are among the first 19 categories on the list (aka Special Exemptions), you stand the best chance of getting into most open tournaments ("open" does not include Majors; The Players; WGC's; invitationals like Bay Hill Memorial Colonial; Tour Championship or Mercedes Championships).
Counting listed names among the first 19 categories (excluded: pre-1970 US Open or PGA Championship winners plus Greg Norman and Tom Watson), and then adding sponsor-foreign invites, PGA of America selections and Open Qualifiers, we arrive at a figure of 104 (as of 5-04-2006). That figure may increase if participating past champions of the particular event being contested (Category 18) are factored in.
When you have open event fields of 144 or 156 to fill, just knowing that you are one of those 104-or-so specially exempt players is very special indeed.
Now, add those in Category-20 "Top 125, previous year's Official Money List", and the count rises to 166. Obviously, the first 40 to 52 players within this group are usually good to go, while the remainder have to wait and see.
Taking it down to Category 25 "Top 20, Previous Year's Nationwide Tour Money List - Top 30 and Ties, Most Recent Q-School", the count stands at 231. If you rank at the top in this category after re-shuffles (order of selection based on money earned in current year) -AND- if some 25-37 other guys (give or take) ranked ahead of you choose not to play that particular week, then you're in the field.
Of course, not everyone of those 231 plays every week, so if you are really way down in the rankings, you might have a better chance getting in every once in a while.
But for sure, it's best to be among the Top 19 categories. That way, there's no doubt.
NOTE: I plan to ask someone at the PGA Tour which categories allow for unlimited sponsor invitation privileges. I already know that being among the Top 150 on the previous year's Money List is one method, and Special Temporary Membership is another.