ORCID has released the ORCID 2017 Annual Report.
Here's an excerpt:
The ORCID Registry officially launched in October 2012. Our member and user base has grown steadily, and as of 31 December 2017, 4,253,582 researchers from every country and discipline had registered for an ORCID iD. We work closely with our community, and are thankful for their continued support and engagement