From 2016 - it's only gotten worse, since then...

https://www.washingtonpost.com/local/social-issues/there-isnt-really-anything-magical-about-it-why-more-millennials-are-putting-off-sex/2016/08/02/e7b73d6e-37f4-11e6-8f7c-d4c723a2becb_story.html