Inventory forecast FAQs
The inventory forecast feature in DFP is a great way to ensure there’s enough inventory available when creating a new line item, or to confirm a saved line item is slated to reach its goal.
When you run a forecast (click either Check inventory or the Delivery forecast tab), DFP is working behind the scenes, running a simulation of the ad server to determine how contending line items will get delivered across the forecasted inventory. Because of subtleties in how DFP simulates the ad server, you may see some numbers that you don’t expect. Following are some of the most frequently asked questions about forecasting.
NOTE: We’re constantly working to improve our forecasting system. If you have questions that aren’t answered below, contact support and include specific numbers, URLs, etc. We’ll analyze your issue and determine if the system is working as intended, or if there’s a way we can update the system to improve the numbers.
DFP forecasts use a sample of the last 28 days of your network’s impression activity as a basis to model future traffic patterns. The forecasting simulation pits the prospective line item for which you’re running a forecast against booked line items, using the 28-day sample as the expectation of how much and in what ways inventory will be available.
Looks at the existing state of the network.
- Runs a simulation for the line item to be forecasted:
- As part of the simulation, DFP first places the line item at a priority lower than the other line items in the network. This artificially lowered priority means that the forecasted line item isn't able to “steal” impressions from other line items.
- Next, DFP runs with the forecasted line item at its given priority.
Analyzes the simulation results to get the estimated forecasting impressions.
The forecasting simulation mentioned above only takes standard and sponsorship line items (guaranteed line items) into account when determining which line item gets allocated for each forecasted impression. Note that guaranteed line items with a status of “Paused” or “Draft”, as well as line items with no creatives, can also be allocated impressions.
For Ad Exchange line items, you can see a forecast of the estimated number of queries that will be available, the number of queries the line item will fill, and the resulting revenue.
Why do two reserved line items with the same targets but different goals have different forecasting numbers?
Even though the line items have the same targeting, the Available, Reserved by same- or lower-priority line items, and Unavailable numbers can be different. This is largely a result of the surpluses and shortages of impressions caused when lowering the priority of a line item for the first step of the forecast simulation (see How does Check inventory / Delivery forecast work?). When that happens, other line items can claim the impressions that otherwise would have gone to the forecasted line item, thus leaving other impressions unused.
Should a forecast over one big date range be close to the sum of multiple, smaller forecasts that cover the same dates?
Let's say you:
Run a forecast from April 1-14.
Then run 14 forecasts — one for each day from April 1-14 — and add the forecasting numbers.
These numbers are actually much closer now because of recent improvements. DFP now analyzes the same set of impressions in steps 1 and 2 above. In the past, the impression sets may have been different, which caused larger discrepancies in the forecasting numbers.
While the numbers are now much closer, they may not exactly match because of factors like frequency capping. For example:
Some reservation has a frequency cap of one impression every 14 days.
A user session has several impressions on each of those 14 days.
The 14-day forecast assigns only one impression in the session, while each one-day forecast might assign an impression.
Example: I made a reservation in March, and it was fully booked. Later, I made a reservation in May, and DFP told me I had to overbook. Why does the May reservation impact my reservation from March?
Our system’s goal is to optimize toward the completion of all existing reservations, so overbooking one reservation impacts all existing reservations that are at equal or lower priority.
Yes, frequency capping is considered. However, because DFP 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 overpredict availability.
Yes, but you first need to traffic at least one saved line item to a user domain target. After 28 days have passed since that first line item was trafficked, the forecasting numbers will be up to date and will fully include user domain targeting.
DFP uses data from the past 28 days to determine a forecast. Therefore, the forecasting numbers will be smaller than expected until 28 days have passed since adding new ad units, or since adding key-values to ad tags on your website. In the meantime, you can manually adjust the forecast in an attempt to get numbers that more closely reflect the new ad units. Note that you can’t directly adjust key-values.
If an ad unit is designated as special, no line item will serve that ad unit unless it’s been explicitly targeted (learn more). Therefore, when you check available inventory for a line item, the forecasting numbers will only include special ad units that have been explicitly targeted.
When you compare future sell-through reports with results from forecasting, keep in mind the differences in the number of creatives. Forecasting is always aware of creatives and assumes by default that the line item will have only one creative on a page (note: as step 6 in this article indicates, you can elect to have the forecasting system consider multiple creatives). In contrast, sell-through reports are not aware of creatives and will report as available all impressions on the page for a given size. Learn about how you can partially counteract this difference, and about more differences between future sell-through reporting and forecasting.
As described under Why don’t forecasting numbers match the future sell-through reports?, there are differences in the ways the numbers are determined for future sell-through reports and inventory forecasting. One difference is that the two sets of numbers are calculated using a different acknowledgment of creatives. The differences can affect several values, including ad units.
I have two line items with the exact same targeting: one is sponsorship, and the other is standard. Why are the matching values the same?
Whether an impression matches a line item depends on the targeting of the line item, and not its type (sponsorship vs. standard), priority, etc.
No. The ad server uses the steps described here to create a plan to pace the delivery of your line items. When determining the pace, the ad server doesn’t consider forecasts from the same system used to check available inventory.
If your network is enabled to use expected traffic shape to help determine pace, the ad server will analyze data to understand how traffic to the targeted inventory will look over the life of the line item. However, this is independent from the forecasts that are used to check available inventory. The main difference is that, with expected traffic shape, future line items are not considered.
Any line item with fewer than 100 contending impressions isn't shown in the list of contending line items. In addition, a maximum of 3000 contending line items can appear on the page.
“Expected to deliver” is calculated differently from “Likely to deliver” and “Available”:
- “Likely to deliver” and “Available” are numbers that can appear when checking available inventory, either through the Check inventory button or Delivery forecast tab. These numbers show the number of impressions your line item is predicted to win without impressions that would be taken away from contending line items. Therefore, these are usually the more conservative numbers, as they don’t take into account impressions that the line item could win when competing against contending line items.
- The “Expected to deliver” column appears on pages that list line items and is part of forecasting for underdelivery. This column portrays the actual number of impressions that this line item is predicted to win, including impressions that would be taken away from contending line items. This is usually the more aggressive number, as it does take into account impressions that the line item could win when competing against contending line items.
We believe it’s useful for publishers to see both of these numbers. If they want to know how many impressions they can book without adversely affecting other line items, they can use the “Available” or “Likely to deliver” number. If they want to know how many impressions the line item is actually going to win, even if it means taking away impressions from other line items, they can look at “Expected to deliver”.
We’re constantly evaluating our forecasting numbers and what they mean to you, to ensure that we’re giving you the most helpful numbers possible. Look for continued improvements to our forecasting numbers in future releases.
If you are running a forecast on optimized pods, ensure you enter the maximum duration of the video VAST ad in the "Max duration (seconds)" field of the line item. This is because optimized pods select video ads based on duration.