It would be strangely quiet. Likely boring, too.
But the point of this video (modified slightly from a three-year-old video by GOOD Magazine) is not about there being only 100 people: 100 is small enough to visualize and understand.
Some of these proportions suffer from rounding more than others, I expect, but it’s still an interesting way to look at who we are as humans and how we share the planet. Another way of considering exactly where we are.