The idea of creating highly targeted ad groups, so that all of the attracted search queries are well aligned with the included text ad copy, is one we’ve written about often.
One of the drivers is the fact that better alignment drives up click-through-rates and thereby quality score.
A number of recent conversations have suggested that this good idea, like many others, is being taken to absurd extremes.
I’m talking about the practice or ‘recommendation’ of limiting ad groups to a single keyword.
Single Keyword Ad Groups Have No Quality Score Advantage
The primary reason I’ve heard for this practice is improved quality score. But it won’t work.
The quality score of a keyword in AdWords is based primarily on the CTR, from a specific geography, of search queries that exactly matches a that keyword. There is an impact from the historical CTR of the entire account, of the relevance of the query-keyword-ad, and the potential of penalties from the landing page. There is no factor in that definition that would favor a single keyword alone in an ad group.
There is no ad group quality score. There is no benefit from keyword loneliness. There is no ‘lots of ad groups’ bonus.
Isolating keywords in-and-of-itself does not help quality score. There is really no way any keyword can impact, positively or negatively, another keyword in terms of quality score.
The Right Number of Keyword Per Ad Group Is…
So how many keywords should be in an ad group?
Assuming we want to maximize quality score and overall results, the answer is: as many as will attract search queries that are directly addressed by your text ads. You may recall that we want to work from the text ad (or text ads) backwards. So the number of keywords really isn’t important. What matters is the alignment of the search queries (and the intents they represent) with the text ads.
If there are a lot of different keywords needed to match and attract all the different search queries that people use to say essentially exactly the same thing, then your ad group should have a lot of keywords. If there is only one keyword that is needed to match and attract to every search query that is directly addressed by the text ads in your ad group, then your ad group should have one keyword.
But the one keyword situation is likely to be very rare.
You don’t want single keyword ad groups, you want single-minded ad groups. If they attract synonymous queries, the more keywords the better.