Here is a bit more information
Turn 1033 - I vote on Worlds Fair proposal
Turn 1034 - I receive word Worlds Fair has passed. I set its production in all my cities. It currently reads 0%.
Turn 1035 - Worlds Fair reads 40% complete. My contribution is 3,296, which is 17%
Turn 1036 - Worlds Fair reads 83% complete. My contribution is 6,327, which is 33%
Turn 1037 - Worlds Fair is complete. Total contribution remains 6,327.
At least some of the AIs contributed on turn 1034, 1035, and 1036. I clearly contributed on only 2 turns. I admit I'm confused by how this works. You can see in that screenshot of the AIs production on turn 1034 that they haven't started building it yet.
Turn 1033 - I vote on Worlds Fair proposal
Turn 1034 - I receive word Worlds Fair has passed. I set its production in all my cities. It currently reads 0%.
Turn 1035 - Worlds Fair reads 40% complete. My contribution is 3,296, which is 17%
Turn 1036 - Worlds Fair reads 83% complete. My contribution is 6,327, which is 33%
Turn 1037 - Worlds Fair is complete. Total contribution remains 6,327.
At least some of the AIs contributed on turn 1034, 1035, and 1036. I clearly contributed on only 2 turns. I admit I'm confused by how this works. You can see in that screenshot of the AIs production on turn 1034 that they haven't started building it yet.