On these figures, Tor could be regularly used by as many as 45.13 million people. Its biggest userbase appears to be in Indonesia, where 21% of respondents said they used the tool, followed by 18% in Vietnam and 15% in India.
Indonesia also has the world's highest penetration of general anonymity tools among its internet users, with 42% using proxy servers or virtual private networks known as VPNs, which disguise the location of the user's internet connection - their IP address - and therefore bypass regional blocks on certain content.
The US, UK, Germany and Ireland meanwhile all report 17% penetration, with Japan the lowest at 5%. The data includes those aged 16-64 for the last quarter of 2013.