Google is rolling out changes for AdWords Impression share reporting (the number of impressions received in a campaign or ad group divided by the estimated number of impressions you were eligible to receive) in AdWords.

Google is adding new columns to separate search and display impression share, as well as hour of day segmentation. Google is also adding the ability to apply filters, see charts and apply automated rules using impression share metrics, and is improving the accuracy of how the data is calculated.

The data is only available going back to October 1.

“Many optimization experts advise a regular review of impression share metrics in well-performing campaigns and ad groups where you want more volume,” says AdWords product manager Dan Friedman. “Use the ‘Search Impression Share’ (or ‘Display Impression Share’ for display campaigns) and look for values below 100%. A lower IS metric means more opportunity for incremental impressions, clicks and conversions.”

“Once you’ve identified well-performing campaigns or ad groups with good growth potential, you’ll want to determine which changes to make to increase your results,” adds Friedman. “Start by looking at the ‘Lost IS (budget)’ (for either Search or Display). This column tells you what percent of the time your ads didn’t appear because your daily budget was insufficient. To reduce lost impressions due to budget, simply raise your daily budget. In general, you’ll end up acquiring more customers at a similar ROI.”

“When you’re satisfied with the results you’re seeing by reducing your ‘Lost IS (budget),’ you can then look at your ‘Lost IS (rank),'” he says. “This tells you what percent of impressions you missed out on due to an ad rank that was too low. To address this, you can optimize to improve your Quality Score or increase your bids. If you decide to increase your bids to increase ad impressions, closely watch how your other key performance metrics like cost per acquisition, profit, and return on ad spend are affected.”

Google is phasing out impression share columns in February. Saved reports will be updated to use the new columns.