Someone asked me this today and truth is there’s no real answer to the question.
It’s not even “just” how many people label email as junk, a lot of people do nothing on receiving the emails and eventually end up deleting them.
So let’s look at the problem in a different light.
Instead of “counting” (or more list, guesstimating) how many people mark emails as junk, unsubscribe, delete them etc let’s look at how many people engage with your emails.
Among others, that has two benefits:
1. It’s a lot easier and accurate to measure. Estimating how many emails end up in the junk folder is very difficult as inbox algorithms change constantly and the provide no feedback on where the email was placed. Measuring engagement in the form of open rates, click through rates, social shares and eventually hard dollar revenue is a lot easier and accurate.
2. It’s a metric that directly ties into your business’ bottom line. What business owners care about at the end of the day (instead of how many people unsubscribed, market the email as spam etc) is how many hard dollars did the email campaign generate and ROI.
Measuring engagement allows you to focus on the positive and relevant side of the equation, revenues.