Msg#: 4064922 posted 6:31 pm on Jan 21, 2010 (gmt 0)
I remember that a general downward trend was often showing up from the very beginning of Google Insights [webmasterworld.com]. That linked thread has some good discussion about what a downward trend doesn't mean - namely, it doesn't necessarily mean fewer searches!
The graphed data is normalized by the total traffic in any region - so a decline on the graph means a declining SHARE of all possible searches. To show a flat graph, a given keyword would actually need to be increasing in volume -- assuming the total volume of all searches is increasing, and for most areas of the world this has been true.