I’m pretty sure you have run into this or will at some point in the future. You send 100 clicks to someone and their stats program says you only sent 94. Or the reverse happens, you are sent 100 clicks but your stats program only shows you receiving 72 clicks. Whose tracking script is right? Most likely both are and here are some of the reasons for discrepancies in counting.
Cookie and IP Tracking
One tracker uses cookie tracking while the other uses IP tracking. Trackers that use pure cookie tracking depend on the user having cookies turned on in his browser. If a user has cookies off, the tracker using cookie tracking can’t count the click as unique. Either it’s just not counted or it’s counted as a unique click even if it’s not.
Internet congestion can also cause counting discrepancies. A click may leave the senders script and while it’s on its way to your tracker it times out, gets lost or hits a downed leg of the Internet and never makes it to its final destination. So the sender counts it but the receiver does not since it never made it.
Auto Redirect Not Completing
A click could be sent from the sender by an auto redirect. If this is the case, sometimes a person closes his browser window before the redirect completes and they see the destination page. In cases like this, the sender counts the click but the receiver does not, since the click never made it.
Server or Router Down
No matter how good your hosting is, regardless if they claim 99.99999% uptime, servers and routers do go down. When this happens, your site is not reachable. The sender counts the click, but since your site is down, it never reaches its destination and is not counted by the receiver.
Overloaded sites can also cause count discrepancies. If the receiving site is currently overloaded and is timing out from time to time, scripts can fail to work. This causes a click to get lost before it makes it through the tracker script to its final destination.
Overloaded mySQL Server
Overloaded shared MySQL database servers can also cause count discrepancies. If a tracker script can’t connect to its database when a click comes through, the click is lost. So, the sender counts the click but the receiver can’t. One way this can happen from time to time is by using a cheap shared hosting account to host a tracker.
ISPs That Use NATs
IPSs that use “Network Address Translation” instead of dedicated IP addresses for surfers can cause click counting discrepancies. Since multiple people connected through the same ISP can be sharing the same IP address, it is possible for two or more people being counted as one person by either the sender or receiver. This is rare but it is becoming more of a problem as NAT is used by more and more ISPs.
Unique Click Counting Techniques
Unique clicks can be counted differently. Some scripts consider a click unique if the same person visits a page within 1 hour. Other scripts consider a unique click a person that visits a page within a 24 hour time period. Other scripts consider a unique click a person that visits a page once in a lifetime. So if a person visits a page and then visits the page again several days later or even hours later, one script may count it as 1 unique click while another script may count it as two or more unique clicks. Scripts that use cookie tracking only can count the same person multiple times as unique if the person has his browser set to clear cookies when his browser is closed. In this case, each time a person starts his browser or restarts it and visits the same page, he is counted as a unique click multiple times.
Over Zealous Click Trackers
Some click trackers block large numbers of IPs claiming they are blocking bots and abusive IP addresses. One popular click tracker goes overboard with this and blocks a large number of ISP IP addresses of real surfers. They claim they are abusive users. Well, I guess they just don’t know that real abusers power cycle their modems to get a new IP assigned to them on a regular basis. Then the blocked IP is assigned to a new user that should not be blocked. But they keep on blocking them. This gets really bad when they block a NAT IP. Now they just blocked thousands of surfers that should not be blocked at all. Eventually they will figure this out when they run out of IP addresses to block and all their click trackers record zero hits all the time. Yes, that last line is a joke but it is to stress a point.
Of course the above list is not exhaustive by any means. There are many more ways that can cause counting discrepancies. The main purpose of this article was to show that counting discrepancies are normal and don’t mean you are being cheated by a sender.
Now if you are having a large counting discrepancy I would first check your site to see if you had any extended down time that it was not reachable. This does happen from time to time. Shoot, some hosting companies even try to hide the fact that your site was down for several hours by saying it must be your Internet connection. Don’t take the word of your hosting company that your site is never down. Look at your stats and bandwidth charts to see if in fact your site was or was not down while a sender was sending clicks.
I hope this has helped you to understand that click counting discrepancies are normal and happen all the time. So don’t go blaming the sender until you eliminate all the possibilities that can cause counting discrepancies first.