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Why Manufacturers Kept Stockpiling After Their Tariffs Got Struck Down
Supply Chain Analytics Pulse
Why Manufacturers Kept Stockpiling After Their Tariffs Got Struck Down
September 2026 | Supply Chain Analytics Pulse
In February 2026, the Supreme Court struck down the legal authority behind most of the tariffs that had pushed U.S. manufacturers into their biggest inventory buildup in a decade. The tariffs were gone within days. The stockpiling was not.
Four months later, GEP’s Global Supply Chain Volatility Index, which tracks tens of thousands of businesses each month, found manufacturers building safety stock at the highest level since January 2023. Shortages of critical inputs hit their highest level since late 2022.
Meanwhile, U.S. factories just posted their strongest month of production since 2021, and the index tracking how “too low” customers’ inventories are sits near a multi-year extreme. A replenishment cycle is forming at exactly the moment safety stock strategy needs to get smarter, not just bigger.
01 Eighteen Months of Tariff Whiplash
The 2025 Buildup
Through 2025, U.S. manufacturers front-loaded raw materials and components like never before. Durable-goods “materials and supplies” inventories hit roughly $221 billion by April, up 3.9% year over year, and total durable-goods inventories climbed for ten straight months, to about $591 billion by July.
Trade uncertainty drove it. NAM’s Outlook Survey found it was manufacturers’ top business challenge all year, cited by 76.2% in Q1 and 73.1% in Q4. By year’s end, 80.3% had paid tariffs on imported inputs, and the Hackett Group put a price on the caution: $1.7 trillion trapped in excess working capital across the 1,000 largest U.S. public companies.
$221B
$591B
inventories by July
$1.7T
trapped in excess working capital
Through 2025, U.S. manufacturers front-loaded raw materials and components like never before. Durable-goods “materials and supplies” inventories hit roughly $221 billion by April, up 3.9% year over year, and total durable-goods inventories climbed for ten straight months, to about $591 billion by July.
NAM respondents expected the buildup to ease slightly, about 0.2%, over the next year. The stockpiling wave, it seemed, had peaked.
The reversal nobody de-stocked for
On February 20, 2026, the Supreme Court ruled 6-3 in Learning Resources, Inc. v. Trump that IEEPA does not authorize the president to impose tariffs, striking down the “Liberation Day” and reciprocal tariffs behind most of 2025’s front-loading. Collection stopped four days later. Refunds are still working through the Court of International Trade.
What replaced IEEPA moved just as fast:
Section 232 tariffs on steel, aluminum, and copper run on separate legal footing and were untouched by the ruling; they remain at 50% on covered articles. What changed, effective April 6, 2026, was scope: many derivative products, parts and components made from those metals, moved to a flat 25% duty on full import value instead of just the metal content, quietly widening exposure for metal-intensive manufacturers.
The data did not cooperate with the “hangover” prediction
Here’s what the original 2025 forecast expected: demand cools, shelves stay full, and 2026 becomes a quiet year of working through last year’s buying. That’s not what happened.
Materials-and-supplies inventories reached $225.5 billion in January 2026, still above where they stood in April 2025. Total durable-goods inventories kept climbing too, up nine straight months to $602.0 billion by June. GEP’s June figures told the same story from the buying side: safety stockpiling back at its highest level since January 2023.
Demand didn’t cooperate either. The ISM Manufacturing PMI hit 55.6% in July, the best reading in four years, while the index tracking customers’ inventories sank to 40.7, deep in “too low” territory.
$225.5B
$602B
durable-goods inventories by June
Put those two trends together and the picture isn’t a hangover. It’s a restocking cycle arriving on top of a warehouse that never actually emptied.
02 What “Segment and Go Dynamic” Actually Delivers: A $9.3M Proof Point
Segment inventory first and make safety stock dynamic rather than static, is not a theoretical improvement. MIT’s Center for Transportation and Logistics ran the numbers on a real network, and they are large enough to change how a safety stock budget gets built.
The sponsor was a U.S. grocery retailer running a hub-and-spoke distribution network that was, by its own admission, missing the mark despite carrying plenty of stock: 57 days of supply for dry food, low inventory turnover, and service levels that still varied widely from node to node. As the business had expanded and SKU counts multiplied, a traditional inventory policy, one set of rules applied network-wide, had stopped working.
Researchers Vi Duong and Nic Holwerda, supervised by Dr. Eva Ponce, modeled 61 SKUs across 31 nodes using a commercial multi-echelon inventory-optimization platform, running 18 scenarios that combined six update frequencies with three service-level targets. Published through Supply Chain Management Review in March 2026, it’s one of the more concrete proof points available for what dynamic, segmented safety stock actually returns:
63%
$9.3M
annual savings on just those SKUs
40%
working capital cut from annual updates
50%+
savings from hub-level nodes
High-variability products benefited the most from frequent updates. Stable, low-variability SKUs saw little additional gain from updating more often than biannually: the highest-value move wasn’t updating everything weekly, it was segmenting products by variability and matching update frequency to each segment.
That last point maps directly onto how tariff-exposed inventory should be triaged. The SKUs and inputs worth a dynamic, frequently recalculated safety stock policy are not the highest-volume ones by default. They are the ones with genuine demand or supply volatility, which, in 2026, increasingly means anything touched by a tariff schedule with a defined expiration date, a single-sourced input, or a lane running through a contested shipping corridor.
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03 Two Sectors, Two Strategies: Automotive’s Live Split Test
Detroit’s three largest automakers spent the first half of 2026 absorbing the same tariff and input-cost environment and arrived at two different buffer strategies, in real time, one of the clearest live comparisons available for how the same volatility produces different inventory decisions depending on where a company’s actual exposure sits.
AutomotiveBuffered
Buffered Against a Single Point of Failure
Ford’s aluminum supply has been constrained for months by fires at facilities owned by Novelis, a key supplier. The company is now facing roughly $2 billion in commodity headwinds this year tied to higher aluminum prices from that disruption, on top of a separate, roughly $1 billion exposure to tariffs that remained in force even after Ford’s projected $1.3 billion refund on invalidated IEEPA levies.
$2B
$1.3B
projected IEEPA refund
$1B
trariffs still in force
The lesson is not that Ford guessed wrong on tariffs. It’s that aluminum, a high-commodity-content input Ford sources heavily and cannot easily substitute, was already the kind of item worth elevated, not blanket, safety stock, and a supplier fire proved the point independently of anything trade policy did.
AutomotiveLean
Betting on Lean insted of Buffered
GM took the opposite approach, describing its strategy explicitly as keeping inventory “lean” to preserve agility: 516,000 units on hand in the first quarter of 2026, a full-year tariff cost estimate revised down to $2.5–3.5 billion, from an original $3.0–4.0 billion, and a roughly $500 million refund of its own forecast.
$516K
$2.5-3.5B
revised tariff cost estimate
$500M
refund forecast
Leaner inventory carries more stockout risk if demand or supply moves suddenly. But for parts and platforms that are not concentrated in a single tariff-exposed input, it also frees working capital that a buffer strategy would otherwise tie up.
04 Safety Stock Readiness Check
Before adding a single unit of buffer inventory, it’s worth an honest look at whether the organization can actually target that buffer, or whether it’s about to repeat the blanket-stockpiling pattern that trapped $1.7 trillion in working capital industrywide.
| Dimension | Early Stage | Developing | Advanced |
|---|---|---|---|
| Tariff & Single-Source Exposure Mapping | No formal mapping of which SKUs or inputs are tariff-exposed or single-sourced. Decisions follow instinct or the last disruption, not a live score. | Exposure tracked for top suppliers and commodities, refreshed after major policy changes rather than continuously. | Every SKU or input carries a live tariff-exposure and single-source risk score that feeds directly into ABC/XYZ segmentation and buffer eligibility. |
| Safety Stock Policy Design | Fixed levels set once and rarely revisited. One formula applied network-wide regardless of demand variability. | Recalculated on a fixed annual or semi-annual cycle. Some segmentation by volume exists, but not by variability. | Recalculated on a cadence matched to each segment's volatility, quarterly or better for high-variance items, biannual for stable ones, not a calendar default. |
| Working Capital Governance | Inventory increases approved ad hoc, with no visibility into carrying cost or the specific risk being hedged. | Buffer inventory has an approval process and is reported, but carrying cost is not weighed against a quantified disruption-avoidance value. | Buffer inventory is funded and reported as a risk-management line item with an explicit reassessment date and a modeled write-down exposure if demand shifts. |
| Regional Policy Differentiation | One global inventory policy applied to every region and business unit. | Regional teams can request exceptions, but there is no structural difference by default. | Inventory and buffer policy differ deliberately by region, reflecting each region's actual demand and trade-policy conditions rather than a single template. |
| Reversal / Destock Signal Monitoring | No defined trigger for reducing stock. Teams learn demand has shifted when a write-down appears in quarterly results. | Basic inventory-to-sales and days-of-supply metrics are tracked monthly, without a defined action threshold. | A named owner monitors leading indicators (inventory-to-sales ratio, new orders, downstream customer inventory indices) against a defined trigger, with authority to act before the write-down stage. |
05 Key Implementation Steps: Choose Your Perspective
Click on the perspective you want to analyze – executives or analysts.
Analyst View

Build a Combined Tariff and Single-Source Exposure Score, Then Re-Rank Your ABC Segmentation
✔ Flag anything scoring high on all three for buffer eligibility, regardless of its existing volume classification.
✔ Re-run the score whenever a tariff authority changes, since the underlying exposure can shift within days.
✔ Combine landed-cost tariff sensitivity, supplier concentration, and lead-time variance into a single score per SKU or input.

Replace Calendar-Based Safety Stock Reviews With a Volatility-Based Cadence
✔ Apply MIT CTL’s finding directly: segment by demand and supply variability, and match update frequency to the segment rather than the calendar.
✔ Model the expected value of moving from annual to biannual updates before recommending anything more frequent.
✔ Prioritize hub-level or upstream nodes first. In the MIT case, more than half of total savings came from correcting overstocking at hubs.

Track the Tariff and Legal Calendar as a Supply Signal
✔ Maintain a simple tracker of tariff-authority expiration dates, pending court rulings, and Section 301/232 actions, feeding directly into the landed-cost model.
✔ Treat each known expiration date as a planning trigger to re-run exposure scores in advance, not a surprise to react to afterward.
✔ Where refunds are pending, track them as a working-capital recovery item, not just a customs footnote.

Watch Downstream Inventory Indices as a Leading Demand Signal
✔ Monitor ISM’s Customers’ Inventories Index and Backlog of Orders Index alongside internal forecasts.
✔ Cross-reference against GEP’s monthly volatility data for regional divergence.
✔ Build the trigger for scaling safety stock up, not just down, since current data points toward a demand-driven restocking cycle forming on top of already-elevated upstream inventory.
Executive View

Require a Tariff-Exposure Segmentation Before Approving Any Blanket Buffer Increase
✔ Score inputs and SKUs on tariff exposure, single-source concentration, and lead-time variability, not on which category asked loudest for more stock.
✔ Reserve elevated safety stock budget for the resulting top tier only. If a request can’t name the specific SKUs it covers, it isn’t ready for approval.
✔ Treat Ford’s aluminum exposure and GM’s lean parts strategy as the same lesson from two directions: the input’s actual risk profile should decide the policy, not company-wide habit.

Separate the Working Capital Conversation From the Resilience Conversation
✔ Fund buffer inventory as an explicit risk-management line, with a stated ROI against a named disruption, rather than folding it into the general inventory budget.
✔ Ask what write-down risk arises if the demand or policy assumption behind a buffer reverses.
✔ Weigh any new buffer request against the $1.7 trillion already sitting in excess working capital industrywide. More stock is not automatically more resilience.

Put a Named Owner on the Reversal Signal
✔ Define the specific trigger, for example a rising inventory-to-sales ratio alongside falling new orders, that would mean it’s time to de-stock, before the buffer is built.
✔ Assign that trigger to one person with the authority to act on it, not a committee that reviews it quarterly.
✔ Revisit the trigger whenever tariff authority itself changes, since a policy reversal can move the underlying risk faster than a normal planning cycle would catch.

Localize Policy by Region
✔ Don’t import a U.S. buffer playbook into Europe or Asia. GEP’s own regional data shows North American and Asian manufacturers building inventory through mid-2026 while European manufacturers were still working through excess stock.
✔ Require regional teams to justify their inventory policy against their own trade-policy and demand conditions, not against head office’s stock.
✔ Build in a standing review point tied to major trade-policy dates rather than a fixed calendar quarter.
06 Conclusion
The last eighteen months did not validate or discredit the manufacturers who built safety stock through 2025. It discredited the idea that safety stock built to hedge one specific policy risk will still make sense once that policy changes, because in 2026, policy changed faster than most inventory plans do.
What held up across that whiplash was not a bigger buffer. It was a better-targeted one. Buffer inventory earns its cost when it’s aimed at something genuinely concentrated, volatile, and hard to substitute. It’s just tied-up cash everywhere else.
The restocking cycle now forming, with customer inventories near multi-year lows and factory output at a four-year high, is the next test of that discipline. It will reward the organizations that already know which SKUs deserve the buffer, and it will quietly cost the ones still deciding that with a blanket policy and a calendar reminder.
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