The company I work for "has ways" to determine ROI; If you buy a car based on an ad you saw a couple weeks ago, they are fairly good about linking those two events in some fashion or another. People smarter than me are working on it. I just work on some of the mundane configuration side of things. It's a bit frightening how good it is.
But are you sure those "ways" are actually effective? I've talked to quite a few laymen recently, including last week a successful marketing professional, who were convinced that read-receipts were an effective way to judge when and how many people read the emails they send. The marketing person was even quoting me general statistics based on this.
But of course not all email clients honor, or even support read receipts. I'm not even sure most of them do. Some folks try to get around this by embedding externally-hosted images, but any good email client shouldn't automatically present those either. So while a "read-receipt" can (probably) be used to tell that some person has at least glanced at your email, they don't really tell you anything about who hasn't.
What I'm at getting here is that marketing people have a nasty tendency to have completely unwarranted blind faith in their tools, when they don't really understand how those tools work and what their actual limitations are. So I really would take any info from them about tech with a grain of salt, no matter how certain they are about it. In fact, the more certain they are, the more suspicious you should be.