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A Search-based Method for
Forecasting Ad Impression in
Contextual Advertising
Defense
Overview
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Background: Web and contextual
advertising
Motivation: importance of volume
forecasting in contextual advertising
Methodology: forecasting volume as
an inverse of the ad retrieval
Experiments
Web Advertising
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Huge impact on the Web and beyond
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$21 billion industry
Main textual advertising channels:
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Search advertising
Contextual advertising
Contextual Advertising (CA)
CA Basics
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Supports a variety of the web ecosystem
Selects ads based on the “context”:
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Interplay of three participants:
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Web page where the ads are placed
Users that are viewing this page
Publisher
Advertiser
Ad network
Advertiser’s goal is to obtain web traffic
Importance of Impression
Volume
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Critical in planning and budgeting
advertising campaigns
Common questions for advertisers and
intermediaries:
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Bid value
Impact of ad variations
Timing of the campaign
A Challenging Problem of
Impression forecasting
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CA platforms are complex systems
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Have hundreds of contributing features
A moving target, dynamic
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Competitors and what they are willing to pay
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Publisher‘s content and traffic vary over
time
Large scale computation: billions of page
views, hundreds of millions of distinct
pages, and hundreds of millions of ads
Dynamic bid landscape
Current practice
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Run test ad in real traffic for a few days
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Simultaneously with the baseline
Compare with the baseline
Obvious drawbacks:
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Use ad serving infrastructure
Expensive
Inefficient
Very long turn-around time
Forecasting as Inverse of Ad
Retrieval
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Ad retrieval: given a page and a set of ads find the
best ads
Forecasting: given an ad and a set of past
impressions, find where the ad would have been
shown if it were in the system
This work: assumes ads selected based on similarity
of features:
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Use the WAND (Broder et al, CIKM 2003) DAAT algorithm as
page selection
Similarity of ad and context feature vectors: requires
monotonic scoring function – this work uses dot product
Features can be based on either user of page context.
Conceptual Work Flow
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Keep all the data used in ad retrieval for a
given period
For an unseen/incoming ad:
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Examine each impression
Score the ad using the ad retrieval algorithm
Compare the ad score with the score of the lowest
ranking ad shown in the page view
Count the impressions where the ad would have
been shown
Main challenge: scale
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In order to beat scalability problem:
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Index only unique pages
Adaptation of the WAND algorithm for
count aggregation needed in forecasting
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A Two-level Process
Use a posting list order to allow early
termination
Indexing Unique Pages
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The revenue estimate of an ad-page pair: score(p,a)
= similarity(p,a)*bid
Revenue estimate for the lowest ranking ad:
minScorep
For repeating pages the similarity is constant
However, ads and bids vary:
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Could change the lowest ranking ad of a unique page
Only one index entry per unique page: What revenue
to store for the lowest ranking ads?
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Save a distribution of estimates {rev1…revn}
Assign median to the minScorep
MinScorep is recomputed based on the current ad supply
Two-level process (Impression
forecasting)
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First phase (approximate) evaluation:
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maxWeightf = max{wf,p : for all p}
Full evaluation:
Framework
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Offline processing
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Online processing
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Analyzing the pages
Building a page inverted index
Creating a page statistics file
We use the inverted page index
and page statistics to forecast
the # of impressions of a given
ad.
Output
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Given a ad and bid, output the
# of imp
Give a ad, output the curve
describe the relation b/w bid
and # of impressions
Experiment Results
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Day to day forecast
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Week to week forecast
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Observations:
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Similar results between day-day and weekweek forecasting.
The errors seems big, however,
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Due to the traffic fluctuation.
Even with large margin of error, our result is
still significant (it’s the best of its kind, and it’s
still acceptable in campaigning budgeting and
advertising strategy)
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Top row has a good prediction.
Bottom row does not match well due to traffic
fluctuation, but match the trend and sharp very well.
Tradeoff b/w efficiency and
accuracy
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Changing the value of minScorep will have effect on
the output of the first level
Ad Variation Example
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Subtle difference could lead to dramatic
performance change
Conclusion
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Ad retrieval algorithm is the determining
factor in the CA impression volume
forecasting
Introduced a search-based forecasting as
inverse of ad retrieval
Promising experimental results
Further work: combine search with learning
approaches to further improve forecasting.