My most educated guess would be 30 percent. I'm assuming there is approximately 235,248,000 people of age to vote in the world. You would need 766,200 of them to petition it. 10 or 20 percent wouldn't work, so I plugged in 25 percent, and it was a little low. After multiplying 30 x 766,200, it was equal to 229,860,000. Therefore, my best guess is 30 percent. I hope I helped! :)