A couple studies are cited in http://www.dailywire.com/news/8054/do-millennials-live-hookup-generation-stereotype-amanda-prestigiacomo http://www.dailywire.com/

A couple studies are cited in http://www.dailywire.com/news/8054/do-millennials-live-hookup-generation-stereotype-amanda-prestigiacomo http://www.dailywire.com/news/8054/do-millennials-live-hooku... and http://www.latimes.com/opinion/opinion-la/la-ol-millennials-less-sex-20160802-snap-story.html http://www.latimes.com/opinion/opinion-la/la-ol-millennials-... Its widely known in the literature.