Is it rare for young adults to avoid social media?

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I recently read some articles stating that employers, psychologists, and psychiatrists believe young adults, specifically towards ages 20 - 33, who avoid social media or don't have social networking accounts such as Facebook and/or Twitter, are considered as "suspicious" or "psychopaths." These theories are based on the recent tragedies of mass shootings in Aurora, Colorado during "The Dark Knight Rises" midnight show and the 2011 massacre in Norway. Both shooters had very little to no digital footprints. What do you think?