Reflections from the River

Singular Vs Plural Keywords: SEO opportunities

Key Message: An SEO strategy that optimised both singular and plural keywords would attract over twice as many search visitors as a strategy focused only on singular keywords.

3rd in a series of 3 posts - in the first post on singular vs plural keywords, I presented evidence to show that searches for singular and plural keywords changes the top ten search results on Google and therefore optimising for both is important. In the subsequent post I showed that whilst there are more than twice as many searches for plural keywords than singular, the opposite effect is found for particular keywords.

In this post the research data collected for the previous analyses will be used to estimate the opportunities available through search engine optimisation of singular and plural keywords.

Let’s consider 4 different SEO strategies regarding singular and plural keywords

1. All singular: optimise the singular version of all keywords - this is quite a likely strategy for anyone who believes that search engines will simply ignore differences between singular and plural keywords;
2. All plural: optimise the plural version of all keywords - this is the strategy likely to have been adopted by people who have seen one of the many reports (example) suggesting that plural keywords are searched for more frequently than singular keywords;
3. Category-specific singulars/plurals: optimise for either singular or plural keywords depending on which predominate within specific categories - e.g. laptop(s), mobile phone(s);
4. Optimised for both singular and plural keywords - for present purposes I will ignore the compromises this may involve and the adverse consequences for other SEO objectives that might ensue.

To make the opportunity analysis feasible and not too assumption-laden, let us simply explore the impact of these 4 strategies on search volumes, using the data collected for the previous post (see research methods). This provided search volumes on 1019 keyphrases that included the singular and plural versions of 7 seed keywords (bed, book, digital camera, laptop, lcd tv, mobile phone and sock).  If fully optimised for both singular and plural keywords (strategy 4), these 1019 keyphrases have a total search volume of 10.6 million searches per month.

Efficiency of different SEO strategies on singular and plural keywords

Optimising for all singular keywords risks losing 64% of the search volume. Optimising for all plurals or on a category-specific basis risks losing 36% and 31% of search volume respectively.  So, for a site that is search engine optimised entirely for singular keywords, optimising for both singular AND plural keywords has the potential to double search traffic.

Singular Vs Plural Keywords: Search Volumes

Key Message: Overall, searchers use plural keywords more than twice as often as singular keywords. For some types of search, however, singular keywords are searched more often (e.g. laptop, mobile phone). The evidence suggests that 3 factors can be used to explain searchers’ preferences for singular or plural keywords: domain factors, linguistic factors and psycho-linguistic factors.

This is the second post in a series of three on singular versus plural keywords - see 1. Singular vs plural: does it matter, 3. Singular vs plural: the opportunity.

We saw in the last post that singular and plural versions of keywords give different search results - optimising for both, therefore, does matter. In this post we start to answer the question ‘how much does it matter’ by considering the search volumes for singular and plural keywords.

Research method

The search volumes for singular and plural versions of keywords was investigated using Google’s Keyword Tool. Seven keywords were selected for this research: bed(s), book(s), digital camera(s), laptop(s), lcd tv(s), mobile phone(s) and sock(s). Five of these were selected because they were the keywords used in Robin Goad’s previous research on singular and plural keywords, which concluded that ‘plural terms are better at sending traffic to retailers than singular terms’. These keywords were: book(s), digital camera(s), laptop(s), lcd tv(s), mobile phone(s). Bed(s) was what started my interest in singular and plural keywords - some data I had from a client project raised some questions I couldn’t answer. And socks was added as a reference keyword: I wanted to explore what the data revealed about keywords with a strong bias in favour of either plurals or singulars - who searches for a single sock? For each of these seven keywords, the singular and plural versions were typed into Google’s Keyword Tool, with the ‘results tailored to’ English, United Kingdom, the ‘match type’ set to exact: the search volumes were recorded from the column titled Local Search Volumes April. The keyword tool returned the top 150 keyphrases containing either the singular or plural version of the target keyword (except laptop(s) where only 119 keyphrases were returned). These were then analysed for:

1. the number of keyphrases containing the singular or plural versions of the target keyword
2. the number of searches conducted for these singular- or plural-version keyphrases
3. the number of searches conducted for the singular- or plural-version keyphrases where both versions of the keyphrase appeared within the top 150 keyphrases (head-to-head comparison)
4. the number of searches conducted for the singular- or plural-version keyword on its own.

Results

Primed with the singular and plural version of 7 different keywords, Google’s Keyword Tool returned 1019 suggested keyphrases. Of these, 509 contained the plural version of the keyword and 510 contained the singular version - as close as it is possible to get to a 50:50 split with an odd number of results! Without the sock(s) keyphrases, which were expected to be strongly biased in favour of plurals, 500 of the top keyphrases were singular (58%) and 369 were plural (42%).  Google’s Keyword Tool reported that 10.6 million searches were conducted for the 1019 keyphrases. Of these searches (again excluding socks), 37% contained the singular-version of the keyword and 63% the plural-version. So, the overall findings from this research reveal that the top keyphrases contain 35% more singular than plural keywords but there is 70% more search volume for the plural keywords. Combining these two statistics to give search volume per keyphrase, there are 130% more searches for each plural keyphrase than there are for each singular keyphrase.

These overall findings, however, conceal some important exceptions. When we look at the number of keyphrases returned by Google’s Keyword Tool for each of our 7 target keywords we see that some are predominantly singular and others are predominantly plural.

Number of keyphrases using singular and plural keywords

There are more singular keyphrases for digital camera(s), lcd tv(s) and mobile phone(s) - bed(s) and laptop(s) have more plural keyphrases, but only just (57% and 54% respectively). Looking at the number of searches changes the predominance of singular and plurals yet again.

Number of searches for singular and plural keyphrases

Whilst 76% of the digital camera(s) keyphrases were singular, 66% of the searches were plural. The pattern for laptop(s) is similar but more modest (54% of keyphrases were plural but 54% of the searches were singular). Generalising patterns of singular and plural keyword use across different types of searches is, therefore, dangerous: searchers change their use of singular and plural keywords according to what they are searching for.

Making sense of how searchers use singular and plural keywords

Looking in detail at the differences between specific keyphrases that are mostly plural and those that are mostly singular suggests that there are 3 types of influences on searchers’ choices of singular or plural - factors I have labelled domain factors, linguistic factors and psycho-linguistic factors.

Domain factors are characteristics of particular domains of knowledge that pre-dispose searchers to use singular or plural keywords. In all the examples discussed here, the domains of knowledge are specific types of products - and it doesn’t take a genius to realise that searches for ’socks’ will substantially outnumber searches for ’sock’ because socks are sold in pairs. The data on sock-related keyphrases confirms this: 93% of keyphrases returned by the Google Keyword Tool and 94% of the search volume for those keyphrases was plural (i.e. socks as opposed to sock). There was only one major exception - searches for sock shop, which is a well known brand.  Similarly, the fact that searches for ‘books’ greatly outnumbered searches for ‘book’ can possibly be explained by domain knowledge about the book market. If I am looking for a specific book I will probably search for it by title or author. Take away these specific searches that would otherwise have used the singular keyword and you are left with predominantly plural keyword searches.  The single exception to this was searches for  ‘phone book’ which had 125 times as many searches as ‘phone books’ but is as much a special case as ’sock shop’ was above. So, knowledge of the domain that searchers are seeking to explore can, in some specific circumstances (sock(s) and book(s), for example) reveal whether singular- or plural-versions of keywords are likely to predominate.

Linguistic factors are the second way of predicting searcher’s preferences for singular or plural keywords. A keyword can be used in two distinct ways for search: it can be the primary search object or it can be the qualifier for a different primary search object. So, for example, if I search for ‘pink laptop’ the thing I am looking for is a laptop and the qualifier I am applying to my search is that I would like the colour of my laptop to be pink. If, on the other hand, I am looking for ‘laptop review’ then the primary object of my search is to find reviews and laptop becomes the qualifier - I want the reviews to be about laptops. Linguistically, the word ‘laptop’ is a noun adjunct within the phrase ‘laptop review’. When keywords are used as qualifiers (noun adjuncts) for a different primary search object, they are nearly always singular.

Keywords are singular when used as a qualifier

A related but different linguistic factor is where the construction of the keyphrase demands the plural version of a keyword to make sense. Searches for ‘lcd tv(s)’ provide a striking example of this.

Search volumes for particular keyphrases containing 'lct tv(s)'

For reasons we will explore within psycho-linguistic factors below, most searches for lcd tv(s) use the singular-version of the keyword. The two exceptions are ‘compare lcd tv(s)’ and ‘plasma and lcd tv(s)’, where plural-versions of the keywords predominate (for ‘plasma and lcd tv(s)’ over 99% of searches were plural). The reasons would seem to be that the keyphrase demands the plural version to make sense: if the phrase was ‘compare lcd tv’ it would appear to beg the question ‘compare with what?’ Similarly, searching for ‘plasma and lcd tv’ suggests an interest in a television that is both a plasma and an lcd device. Searching for ‘plasma and lcd tvs’ indicates and interest in both types of television. Finding keyphrases, such as these, where grammar requires a plural keyword within a category of search terms that are otherwise singular could provide a useful niche for search engine optimisation efforts.

The linguistic factors described above are concerned with the grammar or syntax of language.  Psycho-liguistic factors, by contrast are concerned with people’s beliefs, expectations or intentions in their use of language. One such factor is whether it is the searcher’s intention to find a single product or a range of products to choose from.

Search intentions affect use of singular or plural keywords

This data shows that searching for ‘cheapest’ or ‘best’ - where the intention is presumably to find a single product - leads to predominantly singular keyword searches. By contrast, searches for ‘cheap’ - where the intention is probably to find a range of products - leads to predominantly plural keyword searches.

Another psycho-linguistic factor appears as though it might resolve one of the mysteries of this research. The data on ‘lcd tv(s)’ stood out for predominantly using singular keywords: 88% of the total search volume reported by Google Keyword Tool was for singular keywords. Also, lcd tv(s) defied the cheapest/best=singular, cheap=plural rule just described above - searches for ‘cheap lcd tv’ outnumbered ‘cheap lcd tvs’ by almost 3:1. So what’s going on here? One possibility is that it is something to do with the particular product category - when people search for televisions they, for some unknown reason, search using singular keywords. If this was the case, the same preference for singular keywords should be found for the keyword ‘television’ (instead of ‘tv’). But it isn’t! In fact it is the opposite - 86% of the search volume reported by Google’s Keyword tool for television(s) used plural keywords. This suggests, therefore that searchers have some form of psycho-linguistic bias against using the plural version of abbreviations such as ‘tv’.

The next post will estimate the search engine optimisation opportunities presented by singular and plural keywords.