In December 2012, we added new columns related to 
impression share to the 
account,
 campaign and
 adgroup performance reports. With the introduction of these new columns, the old ones are now obsolete and will be removed as 
previously announced.
The following columns will no longer be available starting February 2, 2013:
- BudgetLostImpressionShare
- ExactMatchImpressionShare
- ImpressionShare
- QualityLostImpressionShare
We recommend reviewing your report definitions to ensure they are up-to-date with the change. As always, please feel free to ask any questions regarding the client libraries or the AdWords API on our 
forum or during scheduled 
office hours. You can also follow the 
Google Ads Developer page for all Ads-related updates.
 - Danial Klimkin, Ads Developer Relations Team.
 - Danial Klimkin, Ads Developer Relations Team.