Delivery basics

How line item delivery is paced

Learn how Ad Manager decides to deliver line items. #lineitems

Pacing is the rate at which Ad Manager delivers impressions for line items. Ad Manager distributes impression delivery based on both the "Deliver impressions" setting for the line items and Ad Manager pacing rules that attempt to optimize delivery. This article describes how line item settings and these Ad Manager pacing rules affect impression delivery.

Monitor your line item's delivery
Use a line item's "Troubleshoot" tab to see reasons your line item isn't delivering. This can help you determine whether your delivery settings need to be adjusted to optimize revenue.

Help me troubleshoot delivery

General pacing rule

Changes to pacing may take up to 48 hours to apply to traffic.

When a line item starts, Ad Manager determines delivery pacing for the line item to ensure it meets its goal. Pacing is affected by the "Deliver impressions" setting for the line item, which allows you to indicate how you want to distribute impressions for a line item over its lifetime.

For line items whose "Deliver impressions" are set to either Frontloaded or Evenly, Ad Manager divides the number of impressions booked for a given line item by the number of days the line item is set to run.

"Expected traffic shape"
"Expected traffic shape" optimizes how line items deliver based on traffic patterns of your site. If turned on, Ad Manager tries to deliver more impressions when traffic is high and fewer when traffic is low. As a result, even if a line item is set to Evenly, you might notice that the absolute number of impressions isn't always identically distributed over time.
View example and illustration

If there were a line item with 7,000 booked impressions that runs for 7 days, whose "Deliver impressions" is set to Evenly, Ad Manager would schedule 1,000 impressions per day, evenly.

Expected traffic shape

"Expected traffic shape" is a network-wide feature that uses past traffic patterns of your site to predict traffic trends and pace delivery accordingly. If you aren't sure that this feature is enabled in your network, check with your Ad Manager administrator or contact Google support.

"Expected traffic shape" versus forecasting

"Expected traffic shape" is different from forecasting. Forecasting considers forecasted traffic patterns accounting for seasonality and forecast adjustments to determine inventory availability and pace delivery. "Expected traffic shape" simply looks at visits to your site to understand when traffic is higher or lower in order to distribute impressions for line items more optimally.

"Expected traffic shape" allows Ad Manager to deliver impressions smoothly relative to the natural traffic fluctuations on your site. There are two ways that "expected traffic shape" analyzes traffic:

  1. Line items running less than two weeks: average of your network's overall past traffic patterns determines when to deliver more or fewer impressions.
  2. Line items running two weeks or more: traffic patterns specific to the inventory a line item targets determines when to deliver more or fewer impressions.
View example and illustration

Example one—line item runs less than two weeks

Suppose you have a new line item that just started today. Ad Manager uses the average of past traffic patterns for your site to determine when to deliver more or fewer impressions for the line item.

This illustration below is an example of how Ad Manager predicts future traffic patterns for a site based on the the past four weeks of traffic patterns. The new line item would the deliver according to that prediction.

  1. New line item delivers based on average page views
  2. Average page views on your site over the past 4 weeks

Example two—line item runs two weeks or more

After a line item runs for two weeks, Ad Manager does a similar analysis based on the specific inventory a line item targets. Instead of site averages, Ad Manager uses averages for the inventory targeted by the line item and looks back up to 4 weeks if the line item runs long enough.

  1. Line item delivers based on page views for inventory targeted
  2. Average page views for inventory targeted by line item running 2 weeks or more

For instance, suppose the line item targeted sports inventory on your site, and currently the Olympic Games are underway. Your sports inventory is getting exceptionally higher traffic as a result. Most of it starts to peak approaching the weekend and peaks during the weekend. As a result, Ad Manager optimizes line item delivery to the sports inventory according to this past traffic pattern. 

Early distribution of impressions

Ad Manager serves more impressions ahead of time to ensure delivery doesn’t fall short of the line item’s goal, due to lack of inventory at the close of the campaign. The “Deliver Impressions” setting controls how aggressively we increase goals early on. Frontloaded shifts line item delivery more aggressively in the beginning of the campaign. Evenly shifts less aggressively.

Example of frontloaded delivery

A campaign goal of 10k impressions (1k per day) over a 10-day period set to Frontloaded, drives the ad server to target 1,400 impressions (1.4Xs the goal) on the first day only. 

"Frontloaded" automatically applies a 40% parameter.

On day two, the 40% parameter is applied to the remaining number of impressions, divided by the remaining number of days. This parameter resets each day until the goal is reached. See the dark green line in Illustration 1 below.

Example of even delivery

A campaign goal of 10k impressions  (1k per day) over a 10-day period set to Evenly, drives the ad server to target 1,050 impressions (1.05Xs the goal) on the first day. 

"Evenly" automatically applies a 5% parameter.

On day two, the 5% parameter resets with the remaining number of impressions divided by the remaining number of days. This parameter resets each day until the goal is reached. See the light green line in Illustration 1 below.


With frontloaded and even delivery, there is a small decrease in impressions served each day as the campaign progresses. Line items set to Frontloaded are more apparent while line items set to Evenly are less apparent as illustrated below.

View illustration: Frontloaded, even and unmodified delivery

  1. Unmodified delivery
  2. Even delivery
  3. Frontloaded delivery

Targeting 40% frontloaded delivery each day means more impressions delivered toward the beginning of the campaign and fewer served at the end. Using this example, roughly 63% of the line item’s total goal will have been delivered over the course of the first half of the campaign.

Applying even delivery to our running example, we get the serving goals illustrated in the chart below:

View illustration: Even delivery

  1. Even delivery with forecasting (5% frontloading)
  2. Forecasted delivery
The graph above represents an account with the Expected Traffic Shape feature active. For more information, please contact your Account Manager.


Ad serving combines traffic shape with the corresponding frontloading factor that's enabled for your network.

Changes over time

Over time Ad Manager has to adjust the goals for your line item based on the actual number of impressions it has served. The originally calculated goals, as outlined above, are only valid when the server delivers exactly to the goal every hour.

Review each step below to see which calculations are updated and modified throughout delivery.

1. Satisfaction Index

Ad Manager calculates a satisfaction index (SI) to measure how far ahead or behind schedule a line item is. Specifically SI measures how well a line item has performed today, relative to the goals set for it by the ad server. The SI is then used during the line item selection process so that line items that are further behind are selected more frequently. If you are not generally familiar with SI and how it is used in the line item selection process, please see the ad selection white paper for more information.

2. SI threshold

Rather than selecting a line item directly based on SI, Ad Manager instead sets a different threshold for each line item. The SI for the line item must exceed this threshold for the ad server to select it among all of the line items that accepted the ad server's request. This threshold is calculated at least once every ten minutes and is controlled by the delivery controller .

The delivery controller attempts to make a line item react to changes in its environment, such as unexpected changes in your site’s traffic levels. Instead of dramatically decreasing the threshold every time the SI starts to fall, the delivery  controller instead takes a more long-term approach. When setting the threshold, the delivery controller considers how far the line item is from a perfect SI and how much time the line item has remaining to meet its goal. The net effect is that your line items will deliver more evenly than they did in the ad server.

Since the delivery controller adjustments are gradual, it will take your line item several hours to fully correct if it gets ahead or behind. Although this may seem odd in the short term, it significantly improves delivery over the life of the line item.

3. Delivery goal recalculation

Ad Manager regularly recalculates the daily and hourly delivery goals. This follows the same process outlined for a new line item above, but uses updated information. Impressions are allocated based on the total remaining impressions and the total remaining time in the line item's campaign. Future delivery goals are updated frequently, and any time that an aspect of the line item that affects budgeting or pacing is modified, such as budget amounts, or start and end-times.

If a line item has fallen behind schedule or has been paused for a period of time, then begins delivering again, Ad Manager tries to make up the missing impressions during the next 24 hours, then deliver the remaining impressions evenly over the remaining days (assuming that the line item is set to deliver evenly). Aggressive catch-up must be activated in Ad Manager ICS for this to happen, otherwise, delivery continues evenly over the rest of the line item. Contact your account team to activate Aggressive catch-up.

For example, a line item has an impression goal of 100,000 over 10 days. The line item delivers its goal of 10,000 impressions on each of the first two days, then is paused for four days. On the seventh day, the line item is restarted; it has 80,000 impressions still to deliver. Ad Manager will try to deliver approximately 50,000 impressions on the seventh day: 10,000 impressions for each day that the line item was paused, plus 10,000 impressions for the current day. (Because of the 5% frontloading that's applied to line items set to spread evenly, the exact impression goal for each day would vary.)

4. Updated by expected traffic shape in pacing

If your network is allowed to pace based on expected traffic (see the section above), the ad server also takes hints from past delivery patterns when determining how many times to serve a line item in a given time window.

For networks that are enabled to pace based on expected traffic, the on-schedule indicator (OSI) will take the traffic-shaped ad server goals into account and will represent a more accurate measure of delivery status. Still, always be sure to check the forecast for a line item before making any delivery changes.

If you recently created your Ad Manager network, wait at least one month before requesting that this feature be turned on.

5. End-of-campaign behavior

During the final hours of a fixed-goal line item that hasn't yet reached its goals, Ad Manager begins adjusting delivery to ensure that the goal is met. In the last hour, a line item that still needs to deliver impressions will function as if it were set to deliver as fast as possible.

If a campaign is behind schedule, it may even serve ahead of higher-priority campaigns that have recently started delivering and are expected to deliver in full.

Why did my line item exceed its limit?

A line item's delivered impressions total might exceed the daily or lifetime cap by a small amount due to delayed impression counting or simultaneous requests that occur as the cap is reached.

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