⚠ A System With No Slack Has No SlackModerate threat

Costco Wholesale (COST) — threat to the moat

Twenty-eight days of stock is an efficiency in a normal year and an empty aisle in an abnormal one — and an empty aisle here is a debit against a fee.

Roughly thirteen inventory turns a year means Costco holds about twenty-eight days of stock1. That is a superb number for return on capital and a thin one for resilience, and the two are the same fact seen from different sides.

Days of merchandise inventoryabout 28 daysCostco, FY202524-30 daysTypical supermarket45-70 daysGeneral merchandiserAbout 13 inventory turns a year on $239,886M of merchandise costs.
Superb for return on capital and thin for resilience — the same fact seen from two sides. An empty aisle here is not a lost sale; it is a debit against a fee the member will be asked to renew.

Costco identifies the exposure itself. It depends on "the orderly operation of the merchandise receiving and distribution process" and disruptions from extreme weather, pandemics, catastrophic events, labour issues, work stoppages or shipping problems "may result in delays in the production and delivery of merchandise to and the operation of our warehouses, which could adversely affect sales and the satisfaction of our members"2. It adds that e-commerce operations "depend heavily on logistics providers, both internal and external."

The membership model raises the stakes above what an ordinary retailer faces. A shopper who finds a supermarket out of stock buys elsewhere that day and returns next week. A member who drives twenty minutes to a warehouse and finds the aisle empty has been given a reason to reconsider a fee they will be asked to renew. Out-of-stock is not a lost sale here; it is a debit against the promise the membership is bought on.

There is a partial offset in the direct-from-producer relationships: Costco does not "obtain a significant portion of merchandise from any one supplier"3 and pursues supply-chain diversification and in-country production. Concentration risk is therefore low even though buffer stock is.

Read merchandise inventories against merchandise costs. Inventories rose to $19,418 million at the third quarter of fiscal 2026 from $18,116 million4 — modest restocking, not hoarding. A sustained jump in days of inventory would mean Costco had concluded the system needed more slack, and it would show up as a lower return on invested capital.

References
  1. Moat Explorer calcRoughly thirteen inventory turns a year means Costco holds about twenty-eight days of stock.
    Moat Explorer calculation: FY2025 merchandise costs of $239,886M over average merchandise inventories of about $18,382M gives roughly 13 inventory turns (about 28 days); accounts payable of $22,363M over inventories of $19,418M gives 115% at Q3 FY2026 — FY2025 and Q3 FY2026 · publ. September 2026 · source ↗
  2. ReportedIt depends on "the orderly operation of the merchandise receiving and distribution process" and disruptions from extreme weather, pandemics, catastrophic events, labour issues, work stoppages or shipping problems "may result in delays in...
    Costco Form 10-K, fiscal year ended August 31, 2025 - Item 1A Risk Factors (U.S. and Canada 86% of net sales and 84% of operating income, California 26% of U.S. net sales, cannibalisation, tariffs, supplier and site-acquisition risk, 'high market expectations') — FY2025 · publ. October 8, 2025 · source ↗
  3. ReportedThere is a partial offset in the direct-from-producer relationships: Costco does not "obtain a significant portion of merchandise from any one supplier" and pursues supply-chain diversification and in-country production.
    Costco Form 10-K, fiscal year ended August 31, 2025 - Item 1 Business (membership counts and renewal rates, warehouse and gas-station counts, under 4,000 SKUs, Executive tier and the 2% reward, human capital and wages, competition, Kirkland Signature) — FY2025 · publ. October 8, 2025 · source ↗
  4. ReportedInventories rose to $19,418 million at the third quarter of fiscal 2026 from $18,116 million — modest restocking, not hoarding.
    Costco Form 10-Q, quarter ended May 10, 2026 - condensed financial statements and notes (total revenue $70,527M, operating income $2,815M, diluted EPS $4.93, balance sheet, segment table, 928 warehouses) — Q3 FY2026 and the first 36 weeks · publ. June 3, 2026 · source ↗
Sources
Generated September 23, 2026