Number Of Keywords Verses Conversion Rates

As promised, whenever I find information that will help you and your business through Creative Marketing, eMail Marketing, and Search Engine Marketing, I'll pass it along. I recently came across this study done by Oneupweb and presented as part of a Master's Thesis. I found the results interesting and thought your web site's search engine optimization could benefit from it.

In 2005, Oneupweb conducted a study to determine if the number of keywords in a search query was related to conversion rates. The hypothesis was that the longer the keyword string, the higher the conversion rate. They focused their study on data generated by natural or organic search engine results listings, not sponsored listings or pay-per-click advertising. (Remember the exercise in our SEO/SEM Conference that one key word would fit into 100 sentences, two key words together would only fit in 10, and three keywords together would only be appropriate in one sentence?)

Using aggregate data collected by ROI trax® (a proprietary search analytics conversion tool designed by Oneupweb), they gathered traffic and conversion data related to search engine keyword searches for the months of July, October and December 2004. Oneupweb ’s database includes data from hundreds of companies, both Business-to-Consumer (B2C) and Business-to-Business (B2B). Some are online retailers, others use websites to generate leads or provide information. All the companies in the study track natural search engine traffic and conversions using ROI Trax tools.

They divided the data into categories by the number of words in the search query; one-word phrases, two-word phrases, three-word phrases, four-word phrases, and five-word phrases. For graphic clarity and because the data volumes were much lower, keyword phrases six words and longer were combined and averaged together. They then calculated the average conversion rate for each category. “Conversion Rate” is defined as the percentage of unique visitors that people are a “that” purchased or converted. Each client in the study defines their specific conversions; for example, some conversions were actual product or service sales, while others valued online actions such as downloading white papers, filling in forms or requesting proposals.

The monetary value of the sale or conversion was irrelevant to the study; they focused on the number of sales or conversions as a percentage of traffic. “Traffic” refers to the number of unique visitors coming to the site for the first time. Repeat visitors aren’t tallied again as traffic and so don’t affect the traffic data of this study. Oneupweb designed a special program to extract ROI Trax data for all of the keywords tracking conversion rates. The program mined traffic and conversion rates from millions of records included in Oneupweb ’s database. The program then divided the data by month into categories based on the number of words in the query (one-word phrases, two-word phrases, three-word phrases, etc.) allowing them to calculate the average conversion rate. The extensive perspective of this data set is important, giving Oneupweb the broadest view of trends from hundreds of thousands of queries.

In addition to using data from all the keyword searches tracked by ROI Trax (Full Database Review), they conducted a more focused analysis of only high-traffic keywords. Oneupweb collected and evaluated traffic and conversion rate data for the top 100 keywords for each company as determined by unique visitor traffic (High Traffic Keyword Analysis). In doing so, they can see if the relationship between keyword length and conversion rate holds for high-traffic keywords. Plus, the focused list allows them to remove mitigating factors.

For example, occasionally a search will return irrelevant results, either from errors the user made in the query or errors the search engine made in interpreting content. Hypothetically speaking, one might type “e-mail marketing ROI optimization” and get Oneupweb information when an e-mail marketing firm would be more appropriate. These erroneous searches and irrelevant search terms have very low traffic, most often. In looking over a month ’s data, one or two unique visitors for a search of this kind is typical. By focusing on the top of the list, we remove the effect of that data.

Figure 1.

2005 OneUpWeb study: Full database

Also, a company ’s name is typically a highly trafficked search term. People searching for a particular company ’s name are predisposed to making a purchase (or conversion) specifically from that company.

This study clearly showed that conversion rates would increase as the number of words in a search query increased. And for the most part, the data confirms the hypothesis. There were two surprises in the data from the Full Database. First, that single-word keywords had a higher conversion rate than two-word keywords, and that after four keywords, the conversion rate dropped. The Figure 1 graph shows just how similar these trends are from month to month. The averages represented are from hundreds of thousands of keyword searches in a single month. Data from all three months shows that single-word keywords have two to five times higher conversion rates than two-word keywords. In October and December, single-word keywords had higher conversion rates than any other category.

To further understand the business impact of keyword length, they also reviewed average traffic per keyword. A review of the Full Database revealed that single-keywords have on average the highest number of unique visitors (Figure 2).

Figure 2.
2005 OneUpWeb study: Average traffic per keyword

The average traffic data for high-traffic Keywords showed a different trend. Single and two-word phrases have very nearly the same average with two-word phrases having slightly more traffic. Generally, shorter phrases had more traffic than longer keyword phrases. The data confirmed the hypothesis and the traffic trend drops steadily as the length of the keyword phrases (or strings) increases (OneUpWeb, 2006).

Based on these findings, Oneupweb is recommending that, for optimal conversion rates, it is worthwhile to focus on expanding optimization to three-word, four-word, and as appropriate five-word strings. Oneupweb is not suggesting companies ignore single keywords in their campaigns —but instead, to add incremental effort to optimizing relevant multi-word keyword strings ranging from two to five words in length.

I hope you found this information useful.

As always, I would be happy to visit you and your organization and make any of the Creative Marketing, eMail Marketing, & Search Engine Optimization / Search Engine Marketing presentations for your team. I am also available for keynotes and consulting. For more information on these and to download other articles, please visit

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Please let me know how I can help you and your organization. Here's wishing you continued success throughout '06.

Lon