Microsoft has given us reason to believe the usage data provided by Xbox API consisted of incomplete estimates of total Xbox Live usage, and does not reflect a complete account of recent usage sessions by the sampled Gamertags. While the data provided seemed reliable in our spot tests, Microsoft tells us the API was "intended to display to each Xbox gamer an approximation of the time spent in a game so that they have the option to compare it with other gamers on the service."

That fault in the underlying data has led us to vastly underestimate total usage times for the apps and games in our usage sample. Graphs and charts that refer to average minutes played or percentage of users who played a game during that 4.5 month period seem to be an order of magnitude lower than the actual per-app usage rates and times. The "My Games and Apps" section of the Xbox One was used by 71 percent of Xbox One players during our sample, according to Microsoft, not the approximately 6.3 percent shown by our data.