Speculation of Google's recent drop in click-through-rates causing a decrease in the organization's stock may have been premature. According to TechCrunch, "Google has made a small change to AdSense that may make a big difference in cutting out errant clicks and even your AdSense revenue. They've redefined the clickable region for Google AdSense from the entire boxed region, to just the text link." The change made by Google resulted in a decrease in clicks, helping to eliminate accidental click-throughs.
While the overall click-through-rate may have decreased, company's relying on Google statistics may be given a more accurate view of ad performance with Google's changes. Ultimately, the decline in CTR is likely due to the change made by Google to deter errant clicks.