- exactMatchImpShare which is the Exact Match IS (measure)
- impShare which is the Impression Share (IS) (measure)
- lostImpShareBudget which is the Lost IS (Budget) (measure)
- lostImpShareRank which is the Lost IS (Rank) (measure)
Jeff Posnick from the Google AdWords API Team said they will likely post on this at the AdWords API blog in the next few weeks.
Forum discussion at Google Groups.