Market Sizing, Honestly

The Missouri Department of Revenue publishes, every quarter, how much taxable sales each county and city in the state recorded. For calendar year 2025, Cape Girardeau County came to $1,785,891,993.43, from quarterly figures of $416.3 million, $449.9 million, $449.8 million and $469.9 million. The fourth quarter shows 1,834 reporting accounts. Butler County, which is Poplar Bluff, came to $832.5 million. Howell County, which is West Plains, $691.8 million. Adair County, which is Kirksville, $448.8 million. The state total was $103,628,761,347.78.

What this is, precisely, before anybody misuses it. It is the sales tax base — the value of transactions subject to county sales tax, as reported on returns, for tax type Sales, with a run date of 17 April 2026. It is not the county economy. It excludes exempt and non-taxable transactions, most wholesale and business-to-business activity, and anything the sales tax does not reach. The file also notes that where six or fewer businesses exist in a category, the financial data is suppressed to protect confidential information. It is a real, legally reported number about a specific thing, which is more than most market figures manage, and it is still narrower than it looks.

Now do the arithmetic that a market-size slide never does. By my calculation, Cape Girardeau County is about 1.7 percent of Missouri's taxable sales. Divide the county's year by its 1,834 fourth-quarter accounts and you get roughly $974,000 of taxable sales per reporting account — a crude average across a hospital gift shop and a car dealership, so treat it as a sense of scale rather than a benchmark. Whatever you sell, your share comes out of that $1.79 billion, and it comes out against 7,490 other registered business locations in the same county.

Which is the honest bottom-up estimate, and it has three steps rather than three acronyms. One: how many potential buyers are inside the distance you will actually travel — households, firms, acres, trucks, whatever your unit is. Two: how much does one of them spend on your category in a year, taken from a real source, or from your own invoices if you have twenty of them. Three: what share could you plausibly serve with the staff and vehicles you have, which for most two-to-twenty person businesses is the binding constraint and never appears on the slide at all. Multiply. The answer will be embarrassingly small compared with anything in a purchased report, and it will be the first market number you have ever had that you could defend line by line.

The contrast across this entry is the argument. The purchased global figure cost $4,150, could not agree with itself about which year it described, and would not tell me how it was made. The Economic Census told me what it counted and when. The Department of Revenue told me what a specific county actually reported, to the cent, for free. The further down you go, the smaller the number gets and the more it constrains — and constraint is the only thing a market size is for.

So the practical version. Download your county from the Revenue file and write the year total at the top of a page. Underneath it, write your own revenue. The fraction is your market share in the only market you can reach, and it is almost certainly a far more interesting number than anything a report was going to sell you. If a lender or a grant reviewer asks for a market size, give them that, with the file name and the run date, and watch what happens.