When you traffic a standard line item, you can specify that its delivery goal and rate be based on viewable impressions as measured by Active View technology. When you select the “Viewable impression” quantity type, you can also set a limit on the total number of impressions served in order to meet that goal.
Create a vCPM line item
- Sign in to Google Ad Manager.
- Create a line item with the following selections:
- Line item type: select Standard.
- Quantity type: select Viewable impressions.
- Rate: set to Viewable CPM by default.
- Impression limit: Enter the number of total impressions you are willing to serve in order to meet the Viewable CPM goal.
The line item stops serving when the impression limit is met, even if the viewable CPM goal has not been met. For example, if you set the “Viewable CPM” goal to 1,000 and “Impression limit” to 1,500, then ad serving stops at 1,500 total impressions, even if only 800 viewable impressions have been served.
For line items with fairly low projected viewability, using this option will reduce impression waste but could cause vCPM line items to under deliver. Therefore, publishers are advised to use this feature judiciously.
How vCPM line items are served and paced
vCPM line item serving uses the historic viewability for your network and predicts what inventory will be viewable for the line item based on its current targeting. Since viewability does not change very much outside of any sudden and drastic changes to a publisher’s page layout or content, this is a sound approach.
Due to how viewability is measured and how various publishers have configured their sites, viewable inventory is often constrained when compared to all inventory, as not all inventory is inherently viewable. As a result, there will be over-delivery of a certain number of impressions associated with vCPM line items.
Example
If a publisher contracts to deliver 100,000,000 viewable impressions, it might actually take 150,000,000 impressions (composed of both viewable and non-viewable impressions) to achieve this goal because the publisher only has a 67% viewability rate.
There seems to be a direct relationship between a publisher’s degree of over-delivery and its overall viewability rate. The higher a publisher’s viewability, the less over-delivery of vCPM line items occurs.
The ad server paces viewable impression line items using the same general pacing methodology it does for impression-based line items, except it uses viewable impressions as the basis for its calculations.
In summary:
- Ad Manager calculates how many viewable impressions it should attempt to deliver per day. This calculation is simply the number of viewable impressions booked for the line item divided by the number of days in the line item's campaign.
- Pacing calculation can change over time as more ad serving data is accrued for the line item. Factors such as satisfaction index (SI) and the remaining time until the end of the campaign can both affect pacing, as can other factors.
