Share of search: what it is and how to calculate it

Share of search is the number of searches for your brand name as a percentage of the searches for all the brands in your category. It is free to measure, quick to update, and in the research that made it popular it tracked market share closely and tended to move before it.

The formula is simple: searches for your brand ÷ searches for all brands in your competitive set × 100.

Where share of search came from

The metric was popularised by Les Binet, then head of effectiveness at the agency adam&eveDDB, at the IPA's EffWorks Global conference in October 2020 (IPA). His slides covered three categories: cars, mobile phones and energy.

What he found:

• Share of search correlated with market share in all three categories.
• It moved first. Changes in share of search led changes in market share by up to 12 months for cars, up to 6 months for phones and up to 3 months for energy.
• The gap was predictive. Binet called share of search minus market share "excess share of search". In his data, brands whose share of search ran ahead of their market share tended to gain share over the following 12 months, a relationship that held for 22 of 23 car brands and 10 of 12 phone brands.
• It has limits. In energy, price mattered so much that forecasting market share from searches was not practical. He expected the same in other categories with short purchase cycles or high price sensitivity.

In 2021 an IPA think tank led by James Hankins of Vizer Consulting looked at 30 cases across 12 categories in seven countries and found share of search represented 83% of share of market on average, while stressing that this was correlation, not causation (IPA).

How to calculate share of search

Two free methods.

Google Trends. Enter your brand and your competitors' brands in one comparison. Google Trends can compare up to 8 groups of terms at once (Google), and scales the results from 0 to 100 relative to each other. Average each brand's values over the period, add the averages together, and divide each brand's average by the total.

Keyword volumes. Look up average monthly searches for each brand term in Google Keyword Planner or an SEO tool, then divide in the same way. This gives absolute numbers, which helps when your brands are too small for Trends to register.

The full method for setting up the comparison is in comparing competitors in Google Trends.

A worked example

Say four meal-kit brands compete in one country, and you pull 12 months of Google Trends data for all four in a single comparison. The figures are hypothetical.

Year 1: 23 ÷ 115 × 100 = 20.0%. Year 2: 30 ÷ 117 × 100 = 25.6%.

Now suppose your best estimate of your market share is 15%. Your excess share of search has gone from 20.0 − 15 = 5 points to 25.6 − 15 = 10.6 points. On Binet's evidence, a widening gap is a sign your sales share is more likely to rise than fall, provided price and availability do not get in the way. Judge the gap against its own history rather than against zero, because each brand's search and sales shares settle at a different ratio.

Share of search vs share of voice

They measure opposite ends of the same process. Share of voice is your slice of the category's advertising or visibility: what you put out. Share of search is your slice of the category's brand demand: what people come looking for. Share of voice is an input you control. Share of search is closer to an outcome.

The share of voice guide covers how to measure that side properly.

Mistakes that wreck the number

Brand names that are ordinary words. If a competitor is called Apex or Bloom, its search volume includes a lot of people who have never heard of it. Use Google Trends topics where they exist, or add a category word and apply it to every brand alike.

Splitting brands across separate comparisons. Trends scales each comparison on its own, so a 40 in one query and a 40 in another are not the same. Keep all brands in one comparison.

Leaving out a competitor. The denominator is the whole competitive set. Drop a rival and everyone's share jumps for no real reason.

Reading single months. A TV campaign or a news story spikes one month. Use rolling averages of 6 to 12 months, as the IPA think tank recommends.

Forgetting existing customers. Binet pointed out that people search for brands they already own as well as ones they might buy. A brand with many customers who reach their account through Google has inflated volume, which is another reason to watch the direction of the gap rather than its size.

Measured the same way every month for a year, share of search becomes one of the few leading indicators a small team can afford. Measured once, it is just a chart.