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.