Test an economic moat with a 10-K: Costco example
A 10-K can support or weaken a competitive-advantage hypothesis, but it cannot prove durability by itself. This dated Costco example tests whether membership behaviour and economics support an advantage, then records what the filing does not settle.
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In this guide
Source and date: Costco Wholesale fiscal 2026 Form 10-K, year ended August 30, 2026, filed October 7, 2026. All company figures below are from that filing, in USD millions where the filing uses that unit. This is an educational example, not a recommendation to trade Costco shares.
Write a hypothesis that could be wrong
Hypothesis: Costco’s membership model and low-price operating approach help retain customers and support recurring fee income. Alternative explanations include store expansion, fee increases and temporary changes in mix or gasoline prices. The goal is to test the claim, not to award a moat label from one metric.
Read the business description first
In Item 1, Costco describes a limited assortment of fewer than 4,000 active core warehouse SKUs and an approach centred on competitive values for members. This describes a strategy; it does not establish that competitors cannot imitate it. Note what evidence would be needed to compare prices and unit costs with rivals, which this filing alone does not provide.
Put the disclosed numbers in a source log
| Observation | What it suggests | What it cannot prove |
|---|---|---|
| Worldwide renewal: 89.8%; US and Canada: 92.3% | Many members renew. | Renewal is a trailing measure, not a same-year causal test of price advantage. |
| Membership fees: $5,907m in 2026 vs $5,323m in 2025 | Fee revenue grew about 11.0%: (5,907 − 5,323) ÷ 5,323. | Growth reflects sign-ups, fee increases and Executive upgrades, not retention alone. |
| Net sales: $297,247m vs $269,912m | Sales grew about 10.1% using the same calculation. | Sales growth includes new warehouses, fuel prices and currency effects. |
| Gross margin: 11.09% vs 11.12% | Reported margin fell three basis points. | It does not isolate merchandise pricing or prove a cost advantage. |
Use the figures in Item 7, Results of Operations, and the membership description in Item 1. The filing says approximately 30% of 2026 membership-fee growth came from the earlier US and Canada fee increase. That is a reason not to attribute all fee growth to a stronger moat.
Look for disconfirming evidence
The filing says worldwide renewal is affected by international membership growth and online sign-ups that renew at a slightly lower rate on average. It also discusses competitive pressure, technology execution and supply risks. A high renewal rate can coexist with a vulnerable advantage. Compare several years, rival disclosures, customer prices and the cost to serve members before making a durability claim. If those comparisons are missing, mark the conclusion provisional.
Make the conclusion narrow and reproducible
Supported by this filing: many memberships renew, fee revenue grew, and Costco reports a limited-assortment, value-led model. Not established: the size, source or future duration of any economic moat relative to competitors. Re-run the same source log after the next annual filing. For the wider process, use the company analysis framework and the definition of an economic moat.
Organise the research trail
MoatCheck helps structure a first pass through public company information. Verify every material claim against the filing and keep contrary evidence visible.
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