To acquire reliable data, researchers at Freie Universität and the University of Arizona surveyed 209 German and 153 American students. The students were asked to specify how narcissistic they find themselves, and their friends were also asked to give assessments. With the agreement of the participants, the researchers were able to access the Facebook profiles of the students and record the status messages they had written in the six weeks prior to the study. It was found that there were no obvious differences between "narcissistic" and "average" Facebook users. “We suspect that posts by narcissistic users attract more attention and are better remembered, which in turn gives the impression that these people post more than others,” says Fenne große Deters, a psychologist at Freie Universität Berlin.
Fenne große Deters, Mathias Mehl, and Michael Eid. 2014. Narcissistic power poster? On the relationship between narcissism and status updating activity on Facebook, in: Journal of Research in Personality, vol. 53, pp.165-174.