apps, allowing for the installation of multiple e-book reading apps. Many Android tablets accept external media and allow uploading files directly onto the tablet's file system without resorting to online stores or cloud services. Many tablet-based and smartphone-based readers are capable of displaying PDF and DJVU files, which few of the dedicated e-book readers can handle. This opens a possibility to read publications originally published on paper and later scanned into a digital format. While these files may not be considered e-books in their strict sense, they preserve the original look of printed editions. The growth in general-purpose tablet use allowed for further growth in the popularity of e-books in the 2010s. In 2012, there was a 26% decline in sales worldwide from a maximum of 23.2 million in 2011. The reason was given for this "alarmingly precipitous decline" was the rise of more general-purpose tablets that provided e-book reading apps along with many other abilities in a similar form factor. In 2013, ABI Research claimed that the decline in the e-reader market was due to the aging of the customer base. In 2014, the industry reported e-reader sales worldwide to be around 12 million, with only Amazon.com and Kobo Inc. distributing e-readers globally and various regional distribution by Barnes & Noble (US/UK), Tolino (Germany), Icarus (Netherlands), PocketBook International (Eastern Europe and Russia) and Onyx Boox (China and Vietnam). At the end of 2015, eMarketer estimated that there were 83.4 million e-reader users in the US, with the number predicted to grow by 3.5% in 2016. In late 2014, PricewaterhouseCoopers predicted that by 2018 e-books would make up over 50% of total consumer publishing revenue in the U.S. and UK, while at that time, e-books were over 30% of the share of the revenue. Until late 2013, the use of an e-reader was not allowed on airplanes during takeoff and landing. In November 2013, the FAA allowed use of e-readers on airplanes at all times if set to Airplane Mode, which turns all radios off. European authorities followed this guidance the following month. E-reader applications Many of the major book retailers and third-party developers offer e-reader applications for desktops, tablets, and mobile devices, to allow the reading of e-books and other documents independent of dedicated e-book devices. E-reader applications are available for Mac, Linux, and PC computers as well as for Android, iOS and Windows Phone devices. Impact The introduction