Understanding the "Time Spent on the Site" Metrics

I have come across this KPI over and over again. Many of my clients want to report it on frequent basis and some even have this as one of their goals for the site. However, I am surprised to find that not many people (not even a lot of web analysts) understand how this metrics is calculated and what this is actually reporting. I am personally not oppose to tracking this metric but have an issue when people try to set goals with respect to improving time on site without knowing what this metrics is actually measuring.

What are the issues with the metrics?
Let�s start with looking at the issues with �Time Spent on the Site� or �Time Spent on a Page� metrics.

1. Last page viewed in a visit is not counted in this metrics
2. Single Page Visits are not counted in this metrics
3. Visitors are multitasking, causing inaccuracies in actual time spent on the site.
4. Tabbed Browsing, causing inaccuracies in actual time spent on the site
5. Download time of the page � Time spent on page calculation includes time taken to download the page.

Let�s cover this one at a time

1. Last page viewed is not counted in the �Time Spent on the Site� calculations. � All most all of the tools (Since I don�t know exactly how many tools are there and how each of them work, I am using almost instead of saying all the tools) use the time lapsed between 2 page requests to calculate �Time Spent on Site�. Since last page viewed does not have any subsequent page request, there is no time lapsed recorded and hence the time spent on last page is not counted in the calculation.
To illustrate let�s take an example of a person viewing page A, B and C
A was requested at 10:00:00 AM
B was requested at 10:00:20 AM
C was requested at 10:00:30 AM
User leaves the site at 10:01:40 (Read page C for 1 Minute and 10 seconds)
Web Analytics Tool will show Avg. Time on Site as 30 seconds instead of 1 min and 40 seconds, the actual time spent by the user.
2. Single Page visits � Since this is the first and the last page viewed by a visitor, as explained above this page views is not counted in �Time Spent on Site� calculations. Single page visits are very common due to search engines and other sites linking deep into the site, this is especially true for content sites (news, articles etc.). Users search or click on links and then read the content spend 5-10 mins and then leave. These users will never be counted in �Time Spent on Page/Site� calculations. If yours is a news/content site then I can assure you that you will be underreporting the time spent on site due to either large percentage of single page visits or the users clicking on few links (within seconds), finding what they are looking for and spending majority of the time (few mins) on the last page and then leaving the site.



Above is the report on a page I created to track timespentonsite.asp, this page was the only page that I viewed in my visit (single page visit), this page shows an AvgTime of 00:00:00 even though I stayed on this page for 5 or so mins. (Snap shot from http://www.USAIndian.net)

3. Visitors are multitasking � Most of the time visitors are multitasking. If they are at work they are doing their regular work, talking to other, getting coffee etc. A visitor opens site, views it for 20 seconds, gets distracted come back 20 mins later, pick up the site where she left, clicks on another link views that for 2 mins, clicks another link views it for 20 seconds and then leaves. Does this happen a lot? You bet, look around talk to your colleagues you will find this happening all the time.
How much time will be reported by web analytics tool? 22 Mins. Is that correct? No. Isn�t the actual time viewed 2 mins and 40 seconds.

4. Tabbed browsing � Tabbed browsing even complicates the issue. Jason Burby�s article http://www.clickz.com/showPage.html?page=3623280 talks about how tabbed browsing has made it much easier to open different page of the site and multiple sites. Jumping to another site, opening various pages of the same site complicates the calculation of time spent on page/site. A visitor comes to the site, within 1 min opens 10 pages in different tabs that he/she wants to view. Now spends 1 hour looking at these pages. What will web analytics tool report as the time spent on site? 1 min, even tough user viewed it for 61 mins.

4. Download times of the pages - If a page takes longer than normal to download it will affect the time spent on the site. User might spend 10 second downloading while only 5 seconds viewing the page, however time spent will show 15 seconds.

So with all these inaccuracies is this metric still useful. I think it still has a value as long as you understand what this metrics is showing.

Sudden changes in time spent could indicate a problem with site navigation, search engine optimization or users behavior. It can shows that one of the factors on your site has changed
a. Single Page Visits � Change in single page visits will affect this metrics. If you search engine rankings have changed that can affect single page visits and hence time spent on site.
b. Navigation on your site � it either is obstructing finding the correct information (time spent goes up) or has improved so users are getting right to they content they are looking for (time spent goes down).
c. Problems with a page � This can cause users to exit site prematurely, causing time spent on the site to go down unless the problem is on one of the pages with very high exit ratio. Since the last page is never counted in calculating time spent, a user who exits after seeing this page or exits after getting an error on this page won�t make much difference in time spent on the site calculations.
d. User Behavior - If nothing else changed, then users might be either multitasking more than before or are using tabbed browsing. This will result in changes in the time spent on the site.