The unfortunate reality is that the deletion of cookies will materially
effect your web metrics and could lead you down the path of bad
decision-making. Here's a list
of what to look out for:
The visitor is
counted as a new visitor no matter how many times they previously
visited your site - This will lead to an overstatement of new
visitors and an understatement of repeat visitors.
You’ll need
to be aware that the metric of average number of visits to become a
customer will be understated. Also if you segment your key
performance indicators (like cost per action) between your new and
returning visitors, the real variance between those two values may not be quite
as high as shown.
Erroneous
conclusions on the behavior of new versus repeat visitors are
possible – Many web analytics applications allow you to
study the paths of your new versus repeat visitors. This can be
especially helpful when trying to determine the aggregate behavior of first
time visitors as they explore your products or services.
Metrics not
applied to correct campaign – When a visitor deletes
cookies, your site has no knowledge of his previous visits and will consider
him a first time visitor. For example, let’s assume the visitor’s first visit is from your
Google AdWords campaign, and the visitor’s second visit, which
leads to a sale is by direct access. If he had deleted his cookies,
the sale will be not be attributed to the Google campaign and will
understate the real performance of that campaign.
Also, if you measure your
AdWords performance by using the “Campaign Summary”
screen within your AdWords account, you need to know that your conversion data may still be inaccurate
even if your visitor
doesn’t eliminate his cookies, since the AdWords
cookie expires 30 days after that last visit.
The longer your
sales cycle, the more inaccurate your statistics will tend to be –
As the amount of time increases between that first visit and the
actual sale, the greater the likelihood that more visitors will
have deleted their cookies.
Google AdWords ad testing - Google has a nice tool for testing different
ad creative within your Ad Groups. If your typical prospect requires
more than 30 days to become a customer, though, the 30-day life of Google's
cookie will tend to lead to inaccurate measurements in ad creative productivity.
A Cookie-Cutter Approach to Accurate Visitor Tracking
There are a couple strategies you can use to minimize the impact on your metrics of cookie removal.
First, using your analytics, cross-reference all 1st time visitors that show no referring URL against your list of historical visitors, by matching the IP addresses. You should be able to do this by downloading a visitor report and exporting to MS Excel. Then sort on IP address.
Now, see if the IP address of any of those 1st time visitors appears in the historical
list of visitors that arrived from a campaign. Where you find a match, you can conclude that it's
quite possible that the visitor associated with that IP address is the same person from the historical list and deleted their cookies. You
should then update your metrics to reflect that finding.
Be careful with this method for these reasons:
In
situations where more than one person uses
the same computer, it's possible that
the subsequent visit is actually a
different person using that same PC, who
indeed may be visiting your site for the
first time.
Many
users do not have a static IP address. If
the computer's IP changes between visits
and the visitor deletes their cookies, you
won't be able to determine they are a
repeat visitor.
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