I used Pinterest's own report https://business.pinterest.com/en/blog/how-to-connect-with-the-deciders https://business.pinterest.com/en/blog/how-to-connect-with

I used Pinterest's own report https://business.pinterest.com/en/blog/how-to-connect-with-the-deciders https://business.pinterest.com/en/blog/how-to-connect-with-t... which pulls that number from comScore apparently. Another report is https://www.statista.com/statistics/408229/us-pinterest-user-gender/ https://www.statista.com/statistics/408229/us-pinterest-user... I'm pretty sure Google Image Search is indeed a major contributor.