The number of impressions you can book depends on how willing you are to displace or preempt existing inventory.
First, run a forecast for the prospective line item. Remember that your line item's trafficking criteria can greatly affect the number of available impressions.
How forecasting accounts for trafficking criteria
Forecasting takes most trafficking criteria into account when determining available inventory, but there are some details you should keep in mind:Frequency capping
Frequency capping is considered. Because DoubleClick for Publishers uses a 28-day sample, monthly or lifetime frequency caps are not captured as part of the sample data. Consequently, in cases with monthly and lifetime frequency caps, forecasting can over predict availability.
Forecasting looks at priority to determine the Reserved for lower-priority line items number--the number of impressions a line item can get if you’re willing to take impressions from lower priority line items. Priority is also taken into account when calculating impressions likely to deliver.
Forecasting ignores this delivery control. Instead, it optimises delivery the best it can. For example, if a line item is set to deliver evenly, the forecast simulation might allocate impressions on a frontloaded basis. In some cases, this can lead to overly optimistic forecasts.
Cost is not a criterion considered in forecasts.
When you run a forecast on answer.py?&answer=79281 road-block ads , DoubleClick for Publishers projects available inventory for all creative sizes in the line item, regardless of whether or not they are served together in a single view.
For example, if you have a line item containing one creative that’s 728 x 90 and one that’s 300 x 250 for three page views, forecast results count one impression for a view in which just the 728 x 90 creative is projected to be served, one for when just the 300 x 250 is projected to be served and two for when they’re projected to be served together (the road block). The forecasting simulation returns a result of four, which accurately simulates how this line item would be served when live, even though there is only one page in which both the 728 x 90 and the 300 x 250 would be served together to the same page.
If you have an ad with multiple creatives of the same size, and you select the “As many as possible” setting for displaying creatives, then forecasting can underestimate the available inventory because it currently assumes every ad has only one creative of a given size. For example, if you have an ad that has two 300 x 250 creatives and a web page with two ad slots of that size, the forecast simulation counts one page view as one impression, whereas in reality, both creatives will be served, making two impressions. So in this case, you should double the number of impressions available to get an accurate count of how many impressions to book safely.
Example: forecasts on line items with multiple creatives of the same size
The table below details expected forecast results, based on the following assumptions:
The website has three pages in the following configuration:
Page one has 3 slots of 300 x 250
Page two has 2 slots of 728 x 90
Page three has 2 slots of 300 x 250 and 1 slot of 728 x 90
Line item delivery is set to "As many as possible".
Creative size(s) No. of creatives Forecast imps Actual imps 300 x 250 1 2 2 300 x 250 2 2 4 300 x 250 3 2 5 300 x 250, 728 x 90 1, 1 4 4 300 x 250, 728 x 90 2, 2 2+2=4 4+3=7 300 x 250, 728 x 90 3, 2 2+2=4 5+3=8
Results on the first page of the forecast provide guidance that can help you decide how many impressions to book.
Available: These are impressions that match the line item’s targeting criteria and are currently unencumbered by obligations to other line items of any priority. Booking this number won't take impressions from other line items.
Reserved for lower-priority line items: These are impressions that can be safely displaced from line items at the same priority as the current line item or taken away from lower-priority line items. Doing so might negatively affect the delivery of these line items.
- Unavailable: Impressions or clicks might be unavailable to this line item for the following reasons:
They're reserved for higher-priority line items.
They're reserved for same-priority line items that can't be displaced to other available inventory.
- Restrictions apply, such as frequency capping for the prospective line item, competitive exclusions, ad exclusion labels, max creatives per page, roadblocking and possibly others.
Matched for specified targeting criteria: The sum of "Available," "Reserved for lower-priority," and "Unavailable." This is the total number of impressions that would be available to the line item if it were unencumbered by other line items and any delivery restrictions, such as frequency capping.
You can also gauge and adjust the effect that booking the prospective line item would have on existing line items by clicking the View contending line items link. Learn more