By Mike Churchill
(Special thanks to my colleagues Jim Gilbert and Liana Evans in researching this article).
There has been a lot of discussion on Google’s recent changes to the way that they handle expanded broad match (at WebMasterWorld , High Rankings Forum and other places).
We have come across a different issue that relates to the investigation of expanded broad match, and has wider-reaching repercussions for your PPC campaigns, as well as understanding oddities in interpreting Analytics. We have been seeing this issue for the last month or so (since Aug-Sep 2007), and according to the Google engineers with which I have discussed this: “the search results […] are the result intended behavior. When determining which ads to show on a Google search result page, the AdWords system evaluates the user’s previous search query as well as the current search query.”
The Google Match Problem
Google is combining the search queries from two successive searches when serving up the PPC ads. If a Google visitor makes a search, then uses the search box on the first search’s results page, the original query AND the second query are BOTH used to determine the ad to display. My colleague Jim Gilbert refers to this as the “Google 1-2 Punch”, and it can end up costing you money and leaving you confused if you don’t take steps to combat this new algorithm change.
Why is this a problem? Ads may be displayed for inappropriate searches, resulting in unnecessary expense for the advertiser.
Examples:
Using Google, search for:
Golf clubs
Then on that results page, search for:
Women’s perfume
Here is what I see:
In another example, I searched for:
mp3
And got these results:
These results look substantially different if I search for:
accessories
And then search for:
mp3
What Is Happening with Google AdWords
If the Google visitor uses the search box from one search to make a second search, when the second request is sent to the Google site, the HTTP_REFERER field is filled in with the URL of the first search request. In this second example, this means that the HTTP_REFERER line in the header would look like this:
GET /search?hl=en&q=mp3&btnG=Search HTTP/1.1
Referer: http://www.google.com/search?hl=en&q=accessories
(There are other lines in the HTTP Request, but these two are the relevant ones.)
I believe that the Google site is seeing the q= parameter from the HTTP_REFERER in addition to the q= parameter from the actual GET request, and is using BOTH terms to determine the relevant PPC ads to display. Note that this issue is NOT reflected in the organic search results.
Try it for Yourself and See
It is easy to reproduce this issue for yourself: Search in one of your current PPC campaigns for a phrase match KW that is at least 3-4 words long (let’s say “Okra ice cream sundae”). (It also works for two word phrases, but this is my example). We want to select a phrase that does not include a shorter phrase that might trigger your PPC campaign. Therefore, insure that the phrase consisting of only the last half of the KW (e.g. “cream sundae”) does not trigger one of your ads. Starting with a newly opened browser, search for the first half of your KW phrase (“okra ice”). Then, using the search box on the results of that query, search for the 2nd half of your KW phrase (“cream sundae”). Your ad should appear (assuming the campaign is active, has remaining budget, etc.,etc.).
This is a factor for broad, phrase, and exact match KW phrases in your AdWords campaigns.
Why do I think it is the HTTP_REFERER field?
The problem is only seen if the visitor uses the form on the results of the first search to perform the second search. If you pass the same two URLs requesting the two searches, but either type the queries manually, cut and paste them, or use a bookmarked query, the organic search results are the same, but the PPC search results reflect ONLY the second query’s terms. In all three of these cases, the HTTP_REFERER is not filled in by the browser when sending the search request.
Insidious Part
Search engine marketers (SEMs) researching the effects of Expanded Broad Match tend to make a lot of back-to-back queries to see which of their PPC ads are being displayed. Since this effect only comes in to play when you make a 2nd search within the search box on the results page of an earlier search, SEMs are likely to have been tripped up by the Google 1-2 punch.
Both expanded broad match and the 1-2 punch have the effect of having an ad displayed for words that are not in the current search query, so many SEMs researching expanded broad match may actually have been seeing the effects of the 1-2 punch instead (or in addition).
What Can You Do About It?
Unfortunately, not a lot. There is nothing in the Google AdWords user interface that allows you to opt out of this new feature (nor the expanded broad match feature, which is dearly desired by many, but is unlikely to happen (See related artcile on Expanded Broad match)
There is a partial defense: the traditional defense against expanded broad match is to use negatives in the campaign to explicitly request that your ad NOT be displayed when one of those related terms is searched for. Thus, if I were selling stainless steel knives, I might include “pots” and “pans” in my negative list to keep my ad from matching to searches for stainless steel pots.
With the Google 1-2 punch, it appears that using a negative exact match phrase in the adgroup may prevent the ad from being displayed – even if that negated phrase is NOT the phrase being searched for in the second case!
For example, I set up a test PPC campaign with a single phrase match KW “okra ice cream sundae”. Searching for “okra ice” followed by “cream sundae” caused my ad to display (as expected). Here is the good news: Adding “–[sundae]” to my negatives list (which should prevent my ad from displaying if someone searched just for sundae also keeps my ad from displaying for the Google 1-2 punch. Curiously, using “-[ice]” keeps the Google 1-2 punch from happening, even if “ice” is not a part of the second search.
This is a work-around, and it will add needless complexity to your PPC campaigns. It will also increase the processing for the Google servers as customers’ negative lists expand extensively to counteract this issue. I firmly believe that the best solution is for Google to give AdWords customers the option of opting out of both expanded broad match and the Google 1-2 punch, and have the Google AdWords system work as advertised.
We will continue to research this issue, and provide updates as we learn more.
