Answer: approximately 9 percent
According to an independent analysis by the University of Pennsylvania — the largest study to ever examine the Kickstarter community — 9 percent of Kickstarter projects failed to deliver rewards.
The study also found that:
Perhaps the most notorious Kickstarter failure was the Coolest Cooler, a decked-out cooler complete with blender, Bluetooth speaker and USB charger, and a cutting board that, back in August of 2014, was the top funded Kickstarter campaign ever. The cooler's creator, Ryan Grepper, raised more than $13 million for his project, breaking Kickstarter's funding record.
But as Mashable reports, almost two years after Coolest's launch on Kickstarter, one one-third of backers have received their coolers, which has sent the crowdfunding concept into a tailspin.