Does the sentence state a fact or an opinion? In a 2013 survey, the majority of college students in the U. S. and Germany said that they preferred reading print books to using digital readers.

Let's be clear here. The sentence is written as a fact; however, whether or not the message IS a fact is unclear without conducting research.

Explanation:

What makes the sentence read as a fact are the words "in a 2013 study."