Local Market Share: How to Estimate Your Slice of the City

"What's your market share?" is a question every business owner can be asked and almost none can actually answer. Not because it's unimportant — it's one of the most useful numbers a business can know — but because the textbook definition requires data a small business will never have access to: your competitors' real revenue, their real customer counts, the true total size of your local market. Here's what's actually measurable, and why a number you can calculate turns out to track one you can't. Why you can't measure market share directly Market share, properly defined, is your revenue (or customer count, or unit volume) divided by the total revenue of everyone competing for the same customers in your area. To calculate it precisely, you'd need to know not just your own numbers — which you do — but every competitor's numbers, which you almost never will. Private local businesses don't publish revenue. Even a rough competitor count requires guessing who's actually competing for the same customers, which is its own research problem (see how to find your real local competitors if you haven't done this yet). So the textbook number is, for almost every small business, permanently out of reach. That doesn't mean the underlying question — "am I winning or losing ground against the businesses actually competing with me" — is unanswerable. It means you need a proxy: something measurable that moves the same direction as market share, even if it isn't the same number. Share of search as a market-share proxy The most useful proxy available to a small business is share of search — the percentage of category-relevant Google searches that go to your brand name specifically, versus your named competitors, over a rolling period. This isn't a guess dressed up as a metric. Les Binet's research, presented at the IPA's EffWorks Global conference and extended in follow-up work by the IPA's James Hankins across 30 case studies spanning 12 categories and 7 countries, found that share of search is a leading indicator of market share — when a brand's share of search rises, its market share tends to follow, and the correlation held strongly enough across categories (automotive, energy, mobile phones, among others) that share of search is now used by marketers specifically because it's measurable in days, from free tools, while real market-share data often takes a fiscal quarter or more to surface, if it ever does. The honest caveat: that research was done primarily on larger, category-level brand competition — not single-location local businesses specifically. The mechanism it relies on — that when people are more inclined to choose a brand, they search for it by name more often — doesn't have an obvious reason to stop working at local scale, but it hasn't been validated the same way for a five-location service business competing in one city. Treat it as a strong, well-evidenced proxy, not a guaranteed one. A simple, honest way to estimate your slice You can't get precise market share. You can get a reasonable estimate, built from numbers you can actually access: Identify your real competitor set. Not every business in your category citywide — the ones actually competing for the same customers you are, by service area and price tier.Pull branded search volume for each one, including yours, using Google Keyword Planner (free with a Google Ads account, no spend required) or Google Trends for relative comparison. Use a rolling 12-month window to smooth out seasonality.Calculate your share: your branded search volume, divided by the total branded search volume across your full competitor set (yours plus theirs). That percentage is your share of search.Track it over time, not as a single snapshot. A single month's share of search tells you relative position today. The trend — rising, flat, or falling over a quarter or two — is what actually correlates with gaining or losing real market share, and it's the more useful number to watch. This gives you something genuinely actionable: not "15% market share" asserted with false precision, but "our share of category search in this city has gone from 18% to 23% over the last two quarters, ahead of our two closest competitors" — a number you can defend, that's trending the direction that matters, and that took an afternoon with a free tool instead of data you'll never get. Where this fits into the bigger picture Share of search is one input, and a strong one, but it's not the whole visibility picture — a competitor can be invisible in search while still winning customers through Google Maps rankings, independent mentions, or recommendations from AI assistants, and vice versa. Measuring search share alone tells you about discovery by name; it doesn't tell you whether you're winning the moments when a customer searches generically, asks an AI assistant, or stumbles on a competitor mentioned in a local forum thread instead. See your share of search next to your named local competitors, alongside where you rank in local Google results, how often you're mentioned independently, and what AI assistants recommend — the fuller picture that search share alone can only hint at. Free report, no credit card, results in about 30 seconds.