Avant garde only increases tourism by 33% if you have no other bonuses to great people generation atall which is extremely unlikely.
I thought historical events were still based around 20% of something over a couple of turns, if that percentage has increased perhaps futurism needs to match the new number.
You actually make a very good point, while its 33% of the base, that doesn't translate into an exact 33% more GP, in fact its likely a lot lower.
Gazebo, is the formula for GP amounts available for VP somewhere I could look at?
According to the Civelopedia (which you so helpfully told me to read), it says roughly 40% of your CPT, as averaged over the last 10 turns of so. I'm pretty sure I've seen late game historic events though higher than my CPT so that doesn't sound right.