Email: Taking Email's Measure
Although click rates tend to have a better correlation to revenue than open rates, click rates on a campaign-by-campaign basis are not very valuable, either. Of course, the better the offer, the higher the click rate. And often, the higher the click rates, the higher the revenue. But you don't need analytics to tell you that—you knew that before you sent the email.
What you want to understand is if you have a portion of your subscribers who open your emails but don't click through to your website. In that case, in my translation of Philip Kotler's "AIDA" model, you seem to have succeeded in getting their attention and interest, but failed in creating enough desire to click through and take action. (Here's a definition of AIDA)
If you have this happening, you need to reconsider your offer and make sure that your subscribers understand that you are a respectable vendor.
On the other hand, if you are actually getting the clicks through to your website, but not getting the conversions, the offer may again be where the problem lies. However, you should also make sure that you are doing everything in your power to reduce the perceived risk of doing business with you. Do you state that recipients' personal information and credit card information are safe? Do you have accreditation from third-party organizations that verify the integrity of your business? This sometimes plays a bigger role than you think.
Continually monitoring your subscriber groups' activity levels over time and using that information to control the frequency and cadence of your email programs will help you with the mission-critical task of getting into your subscribers' inboxes, as well as maximizing the benefits of your email programs. Once you are in the inbox, use your analytics to learn more about your audience—where they are in the customer lifecycle or purchase funnel and what data you could use to move the needle even further. This will help you maximize the monetary value of your subscribers and keep your list healthy.