Inside AdWords: Impression share changes are coming next week. Download any desired historic reports now.On October 1st, we announced several improvements and changes for AdWords impression share (IS) reporting planned to happen in early November. When we launch these improvements next week, there will also be changes to the availability of historical IS reporting data.
Preserving pre-October 2012 historical IS data
If you rely on historical impression share data for reporting or decision making, please download all desired historical IS reports immediately. In a few days, you’ll only have access to historical IS data dating back to October 1, 2012.
Posted by Dan Friedman, AdWords Product Manager