Google declined to give the number of downloads of Google Wallet, which is available as a download from Google Play. (It is region-controlled, and so cannot be installed on devices outside the US.) The current number of downloads shows as between 10m and 50m - offering a wide margin for error. However, based on download figures on the Google Play store, the total installed base is less than 20m. Download milestones recorded on the Internet Archive show that it passed 1m in August 2012, 5m download by March 2013 and passed 10m downloads between 4 October and 9 October 2013. Based on that data, the growth in downloads fits a straight-line extrapolation, which yields this graph: Google Wallet downloads can be estimated by a straight-line graph fitted to its download milestones recorded in the Internet Archive. By September 2014, they would be below 20m. Photograph: Guardian That suggests that there have been fewer than 20m downloads of Google Wallet. Although it comes preinstalled on the Nexus line of phones, those have had comparatively low sales - in the single-digit millions in the US - suggesting 20m as the maximum number in use. Google declined to comment on the Guardian estimate. However, sources with authoriative sources at the company indicated that it is “not far away from the truth” and that 20m is viewed there as “actually a good number”.

http://www.theguardian.com/technology/2014/sep/25/google-wallet-apple-pay-nfc