taberstruths - 9:42 pm on Jun 2, 2013 (gmt 0)
The phenomena can be explained a couple of ways.
1. Google's serp layout has evolved to keep most serp traffic on Google rather than send it off site.
2. Adwords are being displayed more prominently in serp results thus resulting in lower ctr in organic searches
3. Google is loosing traffic to other websites or people going directly to the site of their choice.