Time on Site is the Denominator

A major media company recently did a major redesign of their web site. When users complained about all the problems, and there were many, the sites (re)designers said the problems were the users' fault for not being familiar with the changes, and they pointed to an increase in the time users were spending on the site as proof that the redesign was successful.

It didn't occur to them that there was another very likely reason for the increased time on the site, namely that users were spending more time on the site because the site was harder to use and harder to navigate. In fact, parts of the redesign increased the number of steps needed to perform a number of common actions, sometimes significantly.

Underlying all this is that this major media company seems to not understand what time on site represents. It's not really their fault. Time on site is a phrase so prevalent these days that it gets 138 million hits on Google.

But here's the pivotal question: does the company get value from users spending more time on the site? In fact, they do not. Think about it this way. Which of the following two customers is more valuable to a clothing store?

• Alex goes to the store, spends an hour trying on pants to find one that fits and looks good, buys the pants and leaves.
• Pat goes to the store, tries on one pair of pants and discovers that they fit and look good, so buys them and leaves five minutes later.

The answer is obviously Pat, who left a happier customer. Because they hadn't spent an extra 55 minutes trying on pants, they are far more likely to buy other things, even before they leave, and they are more likely to tell their friends about their good experience.

If the store had measured time in store, they would have thought that Alex was a happier and better customer!

Time on site is still useful to measure — but in a different way. Here are two straightforward equations:

value received by users  time on site

value received by site (e.g., ad revenue)  time on site

Notice that time on site is the denominator in both equations. The first roughly measures how well you're satisfying your users while they're on your site, while the second roughly measures income over time.

Having visitors to your brick and mortar store costs you money, in terms of employee costs, utility costs, etc., even if the visitor buys nothing. The more visitors you have, the more employees you need, even if the visitors buy nothing. The same is true of your web site. Every minute somebody spends on your web site costs you for server time. Although the absolute cost may be smaller, it is not zero. The formulas above are obvious when you think about that plus the old standard ROI, or return on investment. If you measure and worry about about the return on investment for time on site, you'll have a much better understanding of how your site is doing.

What if you have an entertainment property? My company, Puzzazz, is a puzzle technology company that has built a popular free puzzle app for iOS. You might think we should measure time in app because more time in the app must indicate happier users. Nope. Take the people who solve just the New York Times crossword in Puzzazz. Some people can solve a Sunday NYT puzzle in a few minutes; others take an hour or more. Can we draw any conclusions about a user's happiness from the time it takes them to solve the puzzle? No. Different users are not comparable to each other for many reasons and doing things like averaging their times across different puzzles to determine value is not mathematically sound. Instead, we can look at things like puzzles per session and puzzles finished divided by puzzles started. Whatever your site or product is, you should spend the time necessary to figure out what the relevant metrics are.

It's certainly true that measuring your site's value and effectiveness is far more complicated than I lay out here. But it is even more complicated than measuring a number like time on site and expecting it to tell you much by itself. Especially when you use it as the numerator instead of the denominator.