E-book purchases via the internet in Germany 2013-2016

Information on base:
German-speaking population ages 14 and older in private households, at main residence in the Federal Republic of Germany.

Information on random sample:
2013: 8,702 respondents, projected to a population of 70.33 million persons
2014: 8,156 respondents, projected to a population of 70.52 million persons
2015: 7,009 respondents, projected to a population of 69.24 million persons
2016: 7,026 respondents, projected to a population of 69.56 million persons
Information on target group: "German-speaking online shoppers":
2013: projected to a population of 43.95 million persons
2014: projected to a population of 44.16 million persons
2015: projected to a population of 45.33 million persons
2016: projected to a population of 47.01 million persons
This question was phrased by the source as follows: "There are a variety of services and products on the internet, which one can use or order and which have to be paid for. There is a selection on this list. Please name all the options of which you would say: 'This is something I do on the internet, I use or buy this online.'
Product: downloading paid e-books."
(Original German question: "Im Internet gibt es ja ganz verschiedene Dienstleistungen, Waren- und Serviceangebote, die man in Anspruch nehmen oder bestellen kann und die man dann bezahlen muss. Hier auf dieser Liste sind verschiedene Angebote aufgeschrieben. Bitte nennen Sie mir alle Punkte, bei denen Sie sagen: 'So etwas mache ich über das Internet, das nutze oder kaufe ich im Internet.'
Produkt: Kostenpflichtiges Herunterladen von E-Books")