Ongoing Google statistics about IPv6 adoption in the Internet.
Google has many visitors and has widely deploed IPV6.
So they started in 2008 to measure how many visitors they had over the next generation internet protocol.
Just to leave a note: This statistics show how many useres visit google (and their services) over IPv6. This means that google does count how many customers of the access-providers have
You can find IPv6 statistics of google under the following Link: https://www.google.com/intl/en/ipv6/statistics.html
Date: 11. Aug 2014