How time on site is calculated and why you should beware of the bounce rate

Is your web site capturing your visitors’ attention?

One of the best ways to tell is by looking at how long they spend on it and, in particular, which pages are keeping their interest the longest.

If they don’t stay long, then maybe people are coming to your site by mistake or the content needs improving. If they are staying a long time but not buying anything, then maybe the information is unclear or people are having problems working the site.

But to make a valid judgement you need to understand how these values are calculated.

How time on site is calculated

Google Analytics only knows when someone loads a web page or clicks on it and triggers more information to be sent back to Google.

So it will know when they arrive on the page and it may receive information that tells it they are still there.

But what Google doesn’t know is if they have left.

To get around this problem Google Analytics makes the assumption that the visitor has finished on a page once they open another page on the same website. It uses the opening time for the next page as the closing time for the previous one.

This works well until the visitor reaches the last page they look at.

Being the last page there is no next-page opened, so Google will not have a leaving time. Hence, the time spent on this page will be excluded from all of the time statistics reported in Google Analytics.

The only exception to this is if there are any interactions on the page set up to be recorded by Google Analytics, such as through event tracking, then it will use the time the last one of these was recorded as the time the visitor left the page.

So we have good information for all except the last pages. But the real problem comes when the last page is also the only page that the visitor looks at.

The affect of bounces on time on site

A bounce is the term used to describe a visit in which the visitor only views one page of a website.

In other words they do not explore the site they just stay on their entrance page.

Because bounce visitors only visit one page, Google Analytics only knows when they arrive and not when they leave. It therefore assumes a nil value for time they are on the page.

For sites with even a moderate bounce rate this can seriously skew any average time on site metric and you might find it makes more sense to exclude these visits when analysing the time on site statistics.

The importance of time on site

Time on site represents direct feedback from your visitors and it is a good barometer for how interesting your visitors are finding your website and how well it is working. But don’t forget to take the bounce rate into account.

Are new and returning visitor numbers accurate?

Have you ever wondered about the accuracy of the visitor statistics reported in Google Analytics?

It is all to do with how Google Analytics collects the visitor data, and that relies on cookies: those snippets of data that websites like to store on people’s computers.

Each time a visitor views one of your website pages, Google Analytics looks to see if they already have a cookie from your website. If it has, the person is a returning visitor. If it hasn’t, it will download a cookie (which contains a unique id) and the person will be treated as a new visitor.


However, this system does have its limitations:

The number of visitors will be overstated…

Google Analytics does not really know who is looking at your website. But what it does know is which browser is being used on what computer.  Cookies are unique to a browser so, for example: if someone first visits your website using their Google Chrome browser and then visits again using Mozilla Firefox on the same computer they would show as two separate visitors.

Nowadays, many people use several different devices for browsing the web. The same person visiting your website first using their office computer, then their smart phone and then their iPad will be recorded as 3 unique visitors.

This will also have the effect of overstating new visitors and understating returning visitors.

Or the numbers of visitors maybe understated…

Some people don’t like cookies and will set their browser not to accept them. In this case the person would not be included in the visitor count at all.

Google Analytics can only download cookies or record information if the browser is running Java. So, if Java is not running then it will not be able to record any information at all about the visit.

Good, but not perfect, data

The visitor statistics in your Google Analytics reports are a guide, a good, but not perfect, count of the total number of people who visited your website and whether they have been there before.

It is worth remembering that the same people visiting you for the first time on different devices or after clearing their cookies will overstate the number of new visits. And, in turn, the number of returning visitors will be understated.

Also, the longer the time period you are looking at the data for, the more likely it is that people have cleared their cookies; in which case the data is less likely to be accurate.

Don’t let this put you off, just learn to take it into account.

Web analytics isn’t about collecting perfect data, it’s about making good decisions informed by the data you have.