13/264 2017, up 13% from the fourth quarter in 2016 and up 26% from the fourth quarter in 2015. Historically, our Premium Subscribers have streamed more than three times the amount of content per month than Ad­Supported Users. With engagement increasing, Premium Churn has continued to trend lower. In the fourth quarter of 2017, Premium Churn was 5.1%, down from 6.0% in the fourth quarter of 2016 and down from 7.5% in the fourth quarter of 2015. Premium Churn is a monthly measure defined as Premium Subscriber cancellations in the quarter indicated divided by the average number of daily Premium Subscribers in such quarter, which is then divided by three months. As our User base matures, and with the growth in higher retention products such as our Family Plan and Student Plan, we believe Premium Churn will continue to trend lower over time. We are currently in 61 countries and territories and are growing in each of our four geographic regions. Europe is our largest region with 58 million MAUs, accounting for 37% of our total User base as of December 31, 2017, an increase of 26% from the prior year. In our North America region, MAUs increased by 23% from December 31, 2016 to December 31, 2017 and now account for 32% of our MAUs. Our two fastest growing regions are Latin America, with 21% of our MAUs, an increase of 37% from December 31, 2016 to December 31, 2017, and the rest of the world, with 10% of our MAUs, an increase of 51% from December 31, 2016 to December 31, 2017. Our Growth Strategies We believe we are still in the early stages of realizing our goal to connect artists and audiences around the world. Our growth strategies are focused on continuously improving our technology and attracting more Users in current and new markets in order to collect more behavioral data, which we use to offer our Users, advertisers, and artists an even better experience. The key elements of our growth strategy are: • Continually Enhance our Platform in Order to Retain and Grow Our User Base . We will continue to (i) invest heavily in research and development, (ii) make strategic acquisitions in order to enhance our product capabilities, and (iii) make our offerings more attractive to existing and prospective Users. We will continue to invest in our artificial intelligence and machine learning capabilities to deepen the personalized experience that we offer to all of our Users. • Further Penetrate our Existing Markets . In aggregate, only 13% of the payment­enabled smartphone users in the 61 countries and territories in which we have active Users use our platform, based on estimates from Ovum, as of December 31, 2017. This statistic is calculated as the number of our Users within a country divided by the total number of smartphone owners in that country. By pursuing initiatives that drive the continued growth of our User base within our existing markets, we hope to take advantage of this current low penetration rate. These initiatives include enhancing our Ad­Supported offering, continuing to improve our playlists, enhancing the personalization of our music delivery, bringing even more artists to our platform, and expanding our content offerings. • Enter New Geographies . In the last two years, we launched Spotify in Japan, Indonesia, and Thailand, and we expect to continue to expand geographically in order to provide Users around the world with full access to the Spotify music catalog. Before launching in a new market, we typically optimize the local Spotify experience for local music preferences. We seek to obtain the rights to popular local content and have local curators where it makes sense. • Continue to Invest in our Advertising Business . We will continue to invest in our advertising products in order to create more value for advertisers and our Ad­Supported Users by enhancing our ability to make advertising content more relevant for our Ad­Supported Users. Offering advertisers additional ways to purchase advertising on a programmatic basis is one example of how we continue to expand our portfolio of advertising products. We also are focused on developing analytics and measurement tools to evaluate, demonstrate, and improve the effectiveness of advertising campaigns on our platform. 6