CPK is a metric introduced by Performics that measures the total cost of ownership for the average keyword.
The report found that keywords that maintain top-ranked search positions the majority of the time drove 70% of conversions (clicks or other actions) in September.
Also, total conversions originating from keywords in a second place or lower ranking rose by nearly 4% from July through September.
The index is based on more than 150 search campaigns currently under management with Performics. The campaigns include e-commerce and lead-based campaigns. More information is available at http://www.doubleclick.com/knowledge_central .