I think emails are most effective if they include their coupon (assuming they are offering a coupon) in the beginning of the subject line, preferably the first few words. Such as “30% Off Today Through…” This is usually the only way a company will grab my attention and I will actually click on their email. For reasons of email subjects being too long, usually half of the subject is cut off, so it’s even more important to include the promotion in the beginning. Also, more recently there have been research saying that because so many people rely on marketing through emails, some physical mail might be slightly more effective due to not as many people sending out mail nowadays. So regular mail sticks out the more people send emails and the less others send physical mail.
Some reasons metrics aren’t as precise are also due to mobile search and inprivate browsing. Inprivate browsing doesn’t leave a trail on your computer, so there are no cookies accepted, and companies will not be able to track what you’re looking at from where and for how long, etc.
Another type of useful analytic tool would be some sort of call tracking. It wouldn’t show improvement for seo rankings, but it would provide helpful insight on ppc ads. This is the most specific analytic tool because it allows room for improvement within your own company, not just showing you numbers of who’s clicking on your link.