75/264 Premium Subscribers were 71 million as of December 31, 2017 and 48 million as of December 31, 2016. This represented an increase of 46% and 71% from the preceding fiscal year, respectively. Our bi­annual global summer and holiday campaigns contributed 20% and 23% of gross added Premium Subscribers during 2017 and 2016, respectively. Further, the launch of the revamped Family Plan in 2016 resulted in another 31% and 22% of total gross added Premium Subscribers during 2017 and 2016, respectively. Ad­Supported MAUs We define Ad­Supported MAUs as the total count of Ad­Supported monthly active users that have consumed content for greater than zero milliseconds in the last thirty days from the period­end indicated. The table below sets forth our Ad­Supported MAUs as of December 31, 2015, 2016, and 2017. As of December 31, Change 2015 2016 2017 2015 to 2016 2016 to 2017 (in millions, except percentages) Ad­Supported MAUs 64 77 92 13 21 % 15 19 % Ad­Supported MAUs were 92 million as of December 31, 2017 and 77 million as of December 31, 2016. This represented an increase of 19% and 21% from the preceding fiscal year, respectively. Growth in Ad­Supported MAUs benefited from our continued investment in driving the rapid growth of our Ad­Supported Service, both through geographic expansion and consumer marketing. The increase also benefited from continued investment in content and features on our platform, including featured playlists, artist marketing campaigns, and original content to drive increased Ad­Supported User engagement and customer satisfaction. Premium ARPU Premium ARPU is a monthly measure defined as Premium revenue recognized in the quarter indicated divided by the average daily Premium Subscribers in such quarter, which is then divided by three months. Annual figures are calculated by averaging Premium ARPU for the four quarters in such fiscal year. The table below sets forth our average Premium ARPU for the years ended December 31, 2015, 2016, and 2017. Year ended December 31, Change 2015 2016 2017 2015 to 2016 2016 to 2017 Premium ARPU € 6.84 € 6.20 € 5.32 (0.64 ) (9 )% (0.88 ) (14 )% For the years ended December 31, 2017 and 2016, Premium ARPU was €5.32 and €6.20, respectively. This represented a decrease of 14% and 9% from the preceding fiscal years. The decreases were due principally to growth of the Family Plan and movements in foreign exchange rates. The table below sets forth our average Premium ARPU for the quarters ended December 31, 2015, 2016, and 2017. Three months ended December 31, Change 2015 2016 2017 2015 to 2016 2016 to 2017 Premium ARPU € 7.06 € 6.00 € 5.24 (1.06 ) (15 )% (0.76 ) (13 )% For the quarters ended December 31, 2017 and 2016, Premium ARPU was €5.24 and €6.00, respectively. This represented a decrease of 13% and 15% from the preceding fiscal year quarters ended December 31. The decreases were due principally to growth of the Family Plan and movements in foreign exchange rates. 68