I appreciate you posting that article.

It confirms that 25-33% standard (at least in a noisy IM vertical)... seems they were seeing 27%-37%.

But also confirms the real purpose of using double opt. Besides being audit proof, it means higher deliverability as any legitimate mailing system will mail double opt on higher priority maintained servers (often called "tier 1 mailings") than the less spam compliant single opt emails.

Thanks again for the article. Brings a lot of value to anyone who reads this discussion.