Databases Reference
In-Depth Information
1. The position of the ad in a list has great influence on whether or not it
is clicked. The first on the list has by far the highest probability, and the
probability drops off exponentially as the position increases.
2. The ad may have attractiveness that depends on the query terms. For
example, an ad for a used convertible would be more attractive if the
search query includes the term “convertible,” even though it might be a
valid response to queries that look for that make of car, without specifying
whether or not a convertible is wanted.
3. All ads deserve the opportunity to be shown until their click probability
can be approximated closely. If we start all ads out with a click probability
of 0, we shall never show them and thus never learn whether or not they
are attractive ads.
8.1.3
Issues for Display Ads
This form of advertising on the Web most resembles advertising in traditional
media. An ad for a Chevrolet run in the pages of the New York Times is a
display ad, and its effectiveness is limited. It may be seen by many people, but
most of them are not interested in buying a car, just bought a car, don't drive,
or have another good reason to ignore the ad. Yet the cost of printing the ad
was still borne by the newspaper and hence by the advertiser. An impression
of a similar ad on the Yahoo! home page is going to be relatively ineffective
for essentially the same reason. The fee for placing such an ad is typically a
fraction of a cent per impression.
The response of traditional media to this lack of focus was to create newspa-
pers or magazines for special interests. If you are a manufacturer of golf clubs,
running your ad in Golf Digest would give you an order-of-magnitude increase
in the probability that the person seeing your ad would be interested in it. This
phenomenon explains the existence of many specialized, low-circulation maga-
zines. They are able to charge much more per impression for an ad than is a
general-purpose outlet such as a daily newspaper. The same phenomenon ap-
pears on the Web. An ad for golf clubs on
sports.yahoo.com/golf
has much
more value per impression than does the same ad on the Yahoo! home page or
an ad for Chevrolets on the Yahoo! golf page.
However, the Web offers an opportunity to tailor display ads in a way that
hardcopy media cannot: it is possible to use information about the user to
determine which ad they should be shown, regardless of what page they are
looking at. If it is known that Sally likes golf, then it makes sense to show
her an ad for golf clubs, regardless of what page she is looking at. We could
determine Sally's love for golf in various ways:
1. She may belong to a golf-related group on Facebook.
2. She may mention “golf” frequently in emails posted on her gmail account.
