If you're allowing a leeway of 20%, then one hundred percent of species that have ever lived are now extinct
The answer is 99%. I allow 20% leeway on all guestimation answers, it is 20% on your answer. So an answer of 98% without the leeway would be incorrect, but with the 20% leeway it would be 99.2 %, within the leeway.
[video]______________________________[/video]