The graph indicates that only 50% of the samples have IPv6. Also consider:
> The graph shows the percentage of users that access Google over IPv6.
About 20% of the world population lives in regions where Google is outright blocked, so the above users with confirmed IPv6 reachability reflects no more than 40% of the world population.
I'd expect that IPv6 deployment will have a long tail end. Countries lower on resources but with relatively modern infrastructure are the ones who will delay the longest in upgrading to IPv6.
> The graph shows the percentage of users that access Google over IPv6.
About 20% of the world population lives in regions where Google is outright blocked, so the above users with confirmed IPv6 reachability reflects no more than 40% of the world population.
I'd expect that IPv6 deployment will have a long tail end. Countries lower on resources but with relatively modern infrastructure are the ones who will delay the longest in upgrading to IPv6.