Question: Is a click-through rate a good measure of e-mail performance?

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Answer: A click-through rate is a measure of how often an e-mail recipient clicks on a link in your e-mail, usually expressed as a percentage of the e-mails sent or opened. It is useful in measuring response when there is a direct call to action in the e-mail that the recipient can accomplish via the Web, such as buying a product online, taking a survey or reading an article.

The virtue of click-through rates is that they are extremely easy to measure in almost any commercial e-mail software. The mechanics are simple. A link in the e-mail is encoded with some kind of unique identifier that varies for each recipient. When the recipient clicks on the link, that unique identifier is transmitted to your (or your e-mail provider’s) database and reported as a click-through for that recipient.

When comparing click-through rates, it is important to understand exactly what is being measured. As indicated above, it is possible to measure click-throughs as a percentage of either opened or sent mail. The difference can be dramatic, so make sure you understand which you are measuring. The definition of sent mail may also vary. It may include or exclude mail rejected by the recipient’s server (bounces) or other mail deemed undeliverable. Depending on your list quality and hygiene practices, this can significantly swing your results.

Click-throughs can also be measured as either aggregate or unique. Unique measures what percentage of the audience clicked at least once, while aggregate includes duplicate click-throughs by the same recipient. Because you are likely to have at least some recipients who click multiple times, be sure you know whether you are measuring unique or aggregate.

While click-through rates are a useful measure of performance in some types of e-mail, the fact that it is so easy to measure can lead to it being overemphasized or misapplied as a metric. Click-through rates measure recipient movement from e-mail to the Web, which is not a good proxy for success in every type of e-mail. Perhaps your e-mail is trying to encourage visits to your retail location, or a call to your salesperson. Some e-mails are purely informational or are meant to raise awareness of the brand, in which case high click-throughs might actually be a negative, indicating you have not done an adequate job in the e-mail copy and the recipient needs further clarification.

In short, measuring click-through rates is not as straightforward as it seems. Be sure to take a close look at those metrics to get optimal feedback from your e-mail campaigns.

Elaine O’Gorman is VP-strategy at Silverpop (, a permission-based e-mail marketing provider that offers a full range of services, including e-mail marketing strategy, campaign management and execution and campaign analytics.

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