indyank - 5:37 pm on Sep 25, 2010 (gmt 0)
Yes I too have seen what linux is explaining here...i had a traffic increase for one of my sites due to a keyword getting more traction in the serps...but after a few days i notice it coming back to the same levels...during this time frame google seems to be adjusting the ranking positions for one another keyword (it could be more as well)..
I saw this other page moving from position 3 to 4 and then to 5 and the traffic is back to the previous levels (slightly on the lower side).
Here is my theory on how google seems to be doing this.
Google has a fairly accurate count of the traffic it drives to every page for any given keyword and at different serp positions (irrespective of whether you use analytics or not). If traffic to a particular page goes up due to some traction for a particular keyword, they then choose to push down one or more pages (ranking for other keywords) by a few positions.This is done to balance the traffic spike...
This balancing act is not done uniformly at all data centers (regions). It knows how to rank the other pages in different regions to do this balancing act. So, if you are tracking the ranking position in one particular region alone, you may not even be aware that this pages has actually gone down a few positions in a few other regions...
The fundamental assumption behind this theory is google has accurate count of traffic it sends to the top 10 or 20 pages (may be even beyond that) for any given keyword.