Hi Kate and thanks for your reply.
I completely agree. Reporting on a keyword basis is a little old hat now and we should look at overall visits to the site along with other pre defined KPI's agreed with our client (nice article Kate). However; the question remains.
Google provide 2 sources of overall traffic volume (GA and WMT) and they seem to show completely different results.
(Copied from above)
Here's another one for 1st May - 25th May:
GA - Organic search - Total sessions - 874
GWT - Search Analytics - Total Clicks - 431 (New System, all filters removed)
GWT - Search Analytics - Total Clicks - 1755 (Old System, all filters removed)
CRAZY RESULTS!
A lot of the data provided by Google is calculated on No of Visits. If the data showing No of visits is incorrect then the rest of the data becomes incorrect. Taking the results above and using GA as a benchmark, the two results shown in WMT are approx 50% more and 50% less than the bechmark. So the results you report could be 50% either side from the actual. Does this make sense? If WMT is more accurate then I would have to recalculate the results provided in GA.
Example (using data above)
if Total Sales = 10
(GA Results of 874) Conversion Rate = 1.14%
(WMT New Results of 431) Conversion Rate = 2.32%
(WMT Old Results of 1755) Conversion Rate = 0.57%
The old saying of "You can't argue with maths" is only applicable if the data you're working with is correct in the first place.