>Sure, and browses which rejects or periodically delete cookies will be counted multiple times
Actually no, they will be counted only once towards the period in which we are counting them (daily or monthly) as long as the IP of the device is the same. Not multiple times. In mobile IPs are shared due to NAT-ing and thus, this method undercounts. 
This is explained in detail here: https://wikitech.wikimedia.org/wiki/Analytics/Unique_Devices/Last_access_solution#Nocookie_Offset



>a device might use multiple browsers (especially the embedded browsers on mobile devices)
This is correct, multiple browsers on one device will be counted multiple times. This is less of a common browsing pattern than using the same method of access every time.

On Tue, Apr 19, 2016 at 3:12 PM, Gergo Tisza <gtisza@wikimedia.org> wrote:
On Tue, Apr 19, 2016 at 11:52 PM, Erik Zachte <ezachte@wikimedia.org> wrote:
Like Nuria said: this is unique devices, not unique people. Many people in the Global North use more than one device to access Wikipedia (desktop, tablet, phone).

Sure, and browses which rejects or periodically delete cookies will be counted multiple times, and a device might use multiple browsers (especially the embedded browsers on mobile devices)... even taking all that into account, a factor of four seems like a large disparity between this data and the audience panel numbers.

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