Summary: Disruption has shifted from an occasional event to a permanent feature of global supply chains, and that change breaks the static safety stock and fixed lead times most inventory plans still rely on. This blog post looks at why "set-and-forget" buffers fall short under constant volatility, why limited supplier visibility makes the problem worse, and what continuous, proactive inventory planning looks like instead.

Key takeaways

• Disruption is now structural, not occasional — so any buffer you set once is already out of date by the time conditions move.
• Static safety stock and fixed lead times create exposure in both directions: stockouts when suppliers slip, and overstock when you guard against risks that no longer exist.
• Most companies can't see past their tier-one suppliers, so they compensate with larger, less precise buffers — substituting volume for information.
• The teams pulling ahead recalculate lead times and safety stock continuously from real performance and variability, and model disruption before it lands.

When did disruption become permanent?

For years, inventory planning rested on a dependable assumption: set your safety stock, lock in your lead times, and revisit them once or twice a year. Disruption was treated as occasional — a port closure, a supplier delay, a difficult season — followed by a return to normal conditions.

That assumption no longer holds. The disruptions of recent years did not give way to renewed stability; they established a new baseline. Inventory buffers that still reflect a calmer era are no longer protecting the business. In many cases, they are working against it.

Recent McKinsey research makes the change difficult to overlook. In a January 2026 report that analyzed 188 KPIs across industries and surveyed 100 global supply chain leaders, the firm characterizes disruption not as an episodic crisis but as a permanent condition of the global economy — the result of a "great trade rearrangement" shaped by tariffs, industrial policy, and geopolitical pressure.

When disruption is continuous, a buffer calculated once becomes a snapshot of conditions that have already changed. The relevant question is no longer whether your assumptions will break, but how quickly you recognize it when they do — and what the lag costs you in the meantime.

Why does set-and-forget inventory fall short?

Static safety stock and fixed lead times were designed for predictable cycles. They assume that demand variability, supplier reliability, and transit times stay within historical ranges. When those ranges shift — as they now do regularly — the underlying calculations drift out of alignment.

The effect runs in two directions at once. Buffers sized for earlier lead times leave you short when a supplier slips, resulting in stockouts. At the same time, inventory held against a risk profile that no longer applies ties up working capital and warehouse capacity. Last year's tariff-driven stockpiling illustrated the pattern: many companies bought ahead to avoid shortages, then watched demand soften, converting precautionary inventory into costly overstock.

What are you buffering against?

A more fundamental problem is that many organizations are buffering against risks they cannot see. McKinsey found that while 95% of companies have visibility into their tier-one suppliers, only 42% can see into tier-two suppliers or beyond — and that visibility has declined since 2022, even as trade tensions intensified.

Inventory cannot be determined with a disruption that remains invisible. In the absence of visibility, teams compensate with larger, less precise buffers, substituting volume for information. The approach is expensive and slow. It leaves the business exposed where visibility is weakest: deep within a supply base that it cannot fully see.

What does dynamic inventory planning look like?

The organizations that adapt most effectively treat inventory policy as something to maintain continuously rather than configure once. They recalculate lead times from actual performance rather than supplier commitments. Companies choose safety stock with real demand and lead-time variability, applied at the segment level rather than through a single rule of thumb. And they model potential disruption in advance, rather than responding only after a shortage occurs.

That final discipline is where many teams have stalled. McKinsey observed that supply chain digitization investments plateaued in 2024 after three years of rapid growth, meaning many organizations are now managing permanent volatility with capabilities they stopped developing. Proactive planning was once a competitive advantage. Today, it increasingly separates the companies that absorb disruption from those disrupted by it.

The bottom line

Stockouts and overstocks are rarely a matter of luck. More often, they are the predictable result of static policies meeting conditions that will not hold still. The remedy is continuously updated planning — the kind that keeps buffers accurate as conditions change and brings the risks hidden a tier or two beyond your direct suppliers into view.

The assumptions you set in a calmer year have an expiration date. The teams that succeed are prepared to revisit them. Smarter supply chains start there.

FAQs

What's the difference between static and dynamic safety stock?

Static safety stock is set once using fixed assumptions and reviewed only periodically, often once or twice a year. Dynamic safety stock is recalculated regularly from current demand and lead-time variability, so the buffer adjusts as conditions change. In a volatile environment, static buffers quickly fall out of alignment, while dynamic ones stay closer to reality.

Why do stockouts still happen when we're carrying plenty of inventory?

Carrying more stock doesn't help if it's based on the wrong risks. When lead times and demand patterns change, buffers measured for older conditions can leave you short on the items that move while you overstock others. Volume isn't the same as accuracy — inventory must be matched to current variability.

How often should safety stock and lead times be recalculated?

It depends on how volatile the item is. Stable, predictable products may only need a quarterly review, while high-variability or fast-moving items benefit from far more frequent updates — in some cases, weekly. The goal is to recalculate based on your business's cadence and actual performance data, rather than treating any figure as fixed.

What is multi-tier supplier visibility, and why does it matter for inventory?

Multi-tier visibility means seeing beyond your direct (tier-one) suppliers into the suppliers that feed them — tier-two and deeper. It matters because disruptions often originate further upstream, where most companies have little insight. Without that view, teams tend to over-buffer to cover unknown risks, tying up cash without meaningfully reducing risk.