A couple of month's ago, I decided to try to determine how the game was calculating the completion percentage.
After starting five new game profiles, and assisted by
Famine, I came to the conclusion that the game was granting completion percentages as follows:
License Tests:
--60 times 0.409667% = 24.58%
Individual races:
--164 times 0.41% = 67.24%
Championship Series:
--20 times 0.41% = 8.2%
Total percent = 100.02%
As
iainoflo85 says above, only bronze is needed for each license test to get the completion percentage, and the Special Events do not affect game progress.
Each Championship Series (there are twenty) only grants 0.41% towards the completion percentage. It does not matter whether the Championship Series has three races, five races or six races (like the Formula GT Series), it still only grants 0.41% towards the completion percentage.
Each individual race (not in a Championship Series) grants the full 0.41%, so the Sunday Cup race at the Autumn Mini Ring grants the same completion percentage as the 24 hour races at La Sarthe or the 24hr Nurburgring race.
Interestingly (which initially made it difficult to follow GT5's calculation

), the game is not rounding up to the next percentage as you advance (for example, the game does not round up from say 9.8% and show 10%). The game will continue to show 9% until the full 10% is reached.
Respectfully,
GTsail