An interesting graphic from Verisign’s new “Domain Name Industry Brief“:
The relevant footnotes are:
5 The total number of gTLDs and their registrations is published through the Centralized Zone Data Service. https://czds.icann.org/en
6 App usage percent in the U.S. is provided by ComScore. http://www.comscore.com/Insights/Presentations-and-Whitepapers/2014/The-US-Mobile-App-Report
7 Google geotargetable domains. https://support.google.com/webmasters/answer/1347922?hl=en
