Acronym

At the MMC Conference, I heard the term "open rate" several times. It's a statistic that really grates on me. It has one teeny tiny use, and it's not at all what it sounds like it should be.

First, it's necessary to understand how open rates are tracked. You, or your email server, have to embed a tiny, usually transparent image into each email. To see the images in an HTML email, your client retrieves the image from the sender's server. Counting the number of times the image is retrieved divided by the number of emails sent that don't bounce back gives you the open rate.

The problem with this approach: users can turn off images. If someone opens your message but does not view the images, you will never know they opened it. And here's the hammer: what's the top business email client? Outlook. Default is for images not to load. Default view is also with a preview pane.

How else do people access their email? On their mobile device. In almost all cases, the default is that images do not load.

There are other problems, too, as the message preview option in some clients can also distort the number in the other direction.

So when you have an open rate of 30 percent, that does not mean that 30 percent looked at the message. Most likely, more people looked at it than that, what is absolutely clear is that you just don't know, unless you do everything in images and do not use text in your emails at all. (Such a decision will give you more accurate statistics, of course the rather nasty tradeoff is that you ensure your message doesn't reach as many people.)

So what is the use of the statistic? Not much really. If you send out a similar message every week, a newsletter for example, and you alter something about it, say you write a snazzy subject, you can tell if that has some impact on the people you send it to. If you go from 30 percent to 40 percent, it tells you that the new way to do subject lines probably gets your message seen by more people.

But that's about it. I don't even think you should use it as a trending statistic. For example, let's say a year ago you averaged a 30 percent open rate, but that rate has slowly declined so that over the last few months you've only averaged 25 percent. By itself that is not cause for concern. It might mean that your recipients have begun reading more email on mobile devices, which are less likely to retrieve the images than other email clients. Instead, you should rely on secondary measures. If you see that drop in open rate, and in every email you advertise a different book, and you're seeing that you're selling fewer books that are marketed in this way than previously, then you may want to rethink the emails to try to devise ways to make them more interesting to open (while also looking for other causes).

So please, stop using this outdated statistic. You want to know if your emails are working? Include links unique to the email, and see if you entice people to click. Or give a unique code for people to use when making a registration or purchase.