Google has recently made improvements in the impression share reporting section of AdWords reporting tools. In an announcement on Google+, it was revealed that new competitive metrics area has been added in AdWords.
The competitive metrics area has keyword level customized columns including search lost IS (rank), search impression share, and search exact match impression share.
Search Lost IS (Rank) – It is the percentage of time for which your ads weren't visible on the Search Network because of poor Ad Rank. In case you run out of budget at any point when the data range is being examined, you will not be able to see Keywords tab.
Search Impression Share – It is the number of impressions that you have received on the Search Network divided by the number of estimated number of impressions you were qualified to receive.
Search Exact Match Impression Share – When the number of impressions on exact match keywords received on the Search Network is divided with the estimated impressions that you were entitled to receive, you get the exact match impression share.Competitive Metrics Added to Impression Share Reporting on Google AdWords!,