Unique Visitors or Visits — which metric should you use?
Since the late 1990’s, Unique Visitors has often been viewed as one of the most strategic web metrics. Countless companies and site operators have insisted on knowing how many unique visitors came to their site on any given day. Most still do today. In general, they are motivated by the belief that Unique Visitors represents how many “people” they are reaching. Taken a step further, they believe this allows them to measure how many unique “prospects” or “customers” they may have.
By contrast, Visits has largely been the neglected stepchild of web metrics. Most folks know it’s there, but many prefer to ignore it in favor of the more popular Unique Visitor metric. Generally speaking, a visit starts when someone reaches your website, and is considered complete after 30 minutes of inactivity. It is also commonly referred to as a “session”.
Now for sake of argument, let’s say you can only report one of these metrics to your executives — which is it going to be? Unique Visitors? or Visits? When working with clients, I’m often asked this question, particularly in the Media and Retail verticals. And my answer?
Visits…always. Sure, call me crazy — but my logic is actually quite simple.
Here are my top reasons for using visits:
1) Visits are more accurate than Unique Visitors.
2) Every Visit represents an opportunity to persuade or convert a visitor to a customer.
3) Measuring visits is based on fairly established industry standards
Now, here are the top reasons I would not use Unique Visitors:
1) Unique Visitors are less accurate than Visits — Most analytics programs, in the absence of cookie setting, fall back on IP address and user agent. This introduces significant variability in your Unique Visitor counts and can skew your true site performance and reach.
2) Unique Visitors mask your true conversion opportunities — Unique Visitors are a superset of Visits and may represent multiple opportunities to convert a customer. As such, using Unique Visitors as the denominator in most performance calculations is actually overstating the effectiveness of your site. For example, if I visit a retail site 4 times in one week, and purchase twice — what is my conversion rate? If you use weekly unique visitors, my conversion rate is 200%. If you use visits, my conversion rate is 50%. Which is a better representation of site effectiveness? Clearly the 50% is much more valuable in understand where your site may or may not be performing optimally. With the 50% conversion metric, I have the opportunity to analyze which visits did not convert…what happened? Is it a navigational issue? A cross-sell problem? Or perhaps a remarketing opportunity? If you used Unique Visitors, you’d never get this visibility.
3) Unique Visitors are subjective — At the end of the day, what is a unique visitor? Is it someone who comes daily, weekly, or monthly? How do you decide on a time frame for uniqueness, and why is this time frame better than any other? Tying into my earlier point about masking your true conversion opportunities, the longer your unique visitor timeframe, the more you effectively overstate success.
4) Unique Visitors aren’t really visitors — Let’s be honest for a moment. Unique Visitors can represent several things. Optimally, a Unique Visitors represents an individual that comes to your website. If you have a strong registration process, like say an Apple iTunes, you could actually achieve this high level of accuracy. However, few sites — even in the media space — have such a luxury. Rather, most sites rely on cookies to measure unique visitors. Well, we’ve all heard about the issues with cookies replacements and deletions, and some cookies are certainly more resilient than others (did you know there are at least 5 different cookie types you can use to track visitors?)
Let’s assume 5% of your visitors delete cookies…that would imply a 5% level of inaccuracy around uniques right? Wrong. The fallback method for unique visitor determination is most commonly IP and user agent string — a *much* less reliable approach than cookies. This was actually a key reason log file solutions fell out of favor — because most relied on IP and user agent and hence were highly inaccurate. Because of the inaccuracy of user and IP agent, your 5% of cookie rejecting visitors can actually skew your traffic numbers by many times over. So you may find that your 5% is actually 15% of your unique visitors. And because it’s nearly impossible to reconcile this number (outside of triangulating with registered user counts), you have little hope in relying on unique visitors as a true measure of “visitors”.
Furthermore, assuming you can set a persistent cookie, you’re only measuring a computer — not a person. Multiple people use single computers. Single people use multiple computers. So what is your true unique visitor count?
To summarize…embrace Visits, steer clear of Unique Visitors
Amidst all this uncertainty around unique visitors, the fact is that I rarely use this metric in my web analysis and optimization efforts. In fact, beware the vendor that says they can provide a “more accurate” unique visitor count than your current vendor — until they can solve for the above issues, it’s useless. Now, there are situations where I do use unique visitor counts — and I’ll talk about those in a future blog entry. In the meantime, my recommendation is always to use Visits — no matter how neglected it may be in your organization! And as always, if you’d like assistance understanding how to leverage web analytics to drive ROI, please do not hesitate to contact the Omniture Best Practices Group.