Here are some statistics that illustrate the scale of what we’re seeing:
76.9% of the emails we received are signed according to the (DKIM) standard. Over half a million domains (weekly active) have adopted this standard. 89.1% of incoming email we receive comes from SMTP servers that are authenticated using the SPF standard. Over 3.5 million domains (weekly active) have adopted the SPF standard. 74.7% of incoming email we receive is protected by both the DKIM and SPF standards. Over 80,000 domains have deployed domain-wide policies that allow us to reject hundreds of millions of unauthenticated emails every week via the DMARC standard.
DKIM is very tough to implement compared to SPF. That huge 74% portion of the pie where both SPF and DKIM are implemented I'm going to assume is primarily people using Gmail/Hotmail/Yahoo mail and the like.
DMARC is something I use on my domains, but I only set it to report, not reject mails. I'm a bit surprised there are 80K domains using DMARC that way.