In the story of how the modern world was constructed, Toyota stands out as the mastermind of a monumental advance in industrial efficiency.

The Japanese automaker pioneered so-called Just In Time manufacturing, in which parts are delivered to factories right as they are required, minimising the need to stockpile them.

Over the past half-century, this approach has captivated global business in industries far beyond autos. From fashion to food processing to pharmaceuticals, companies have embraced Just In Time to stay nimble, allowing them to adapt to changing market demands, while cutting costs.

But the tumultuous events of the past year have challenged the merits of paring inventories, while reinvigorating concerns that some industries have gone too far, leaving them vulnerable to disruption.

As the pandemic has hampered factory operations and sown chaos in global shipping, many economies around the world have been bedevilled by shortages of a vast range of goods - from electronics to lumber to clothing.

In a time of extraordinary upheaval in the global economy, Just In Time is running late.

"It's sort of like supply chain run amok," said Professor Willy C. Shih, an international trade expert at Harvard Business School. "In a race to get to the lowest cost, I have concentrated my risk. We are at the logical conclusion of all that."

The most prominent manifestation of too much reliance on Just in Time is found in the very industry that invented it: Automakers have been crippled by a shortage of computer chips - vital car components produced mostly in Asia.

Without enough chips on hand, auto factories from India to the United States to Brazil have been forced to halt assembly lines.

But the breadth and persistence of the shortages reveal the extent to which the Just in Time idea has come to dominate commercial life.

This helps explain why Nike and other apparel brands struggle to stock retail outlets with their wares. It is one of the reasons construction companies are having trouble purchasing paints and sealants. It was a principal contributor to the tragic shortages of personal protective equipment early in the pandemic, which left front-line medical workers without adequate gear.

Just In Time has amounted to no less than a revolution in the business world. By keeping inventories thin, major retailers have been able to use more of their space to display a wider array of goods. Just In Time has enabled manufacturers to customise their wares. And lean production has significantly cut costs while allowing companies to pivot quickly to new products.

These virtues have added value to companies, spurred innovation and promoted trade, ensuring that Just In Time will retain its force long after the current crisis abates.

The approach has also enriched shareholders by generating savings that companies have distributed in the form of dividends and share buybacks.

Still, the shortages raise questions about whether some companies have been too aggressive in harvesting savings by slashing inventory, leaving them unprepared for whatever trouble inevitably emerges.

"It's the investments that they don't make," said Professor William Lazonick, an economist at the University of Massachusetts.

The shortages in the world economy stem from factors beyond lean inventories. The spread of Covid-19 has sidelined port workers and truck drivers, impeding the unloading and distribution of goods made at factories in Asia and arriving by ship to North America and Europe.

The pandemic has slowed sawmill operations, causing a shortage of lumber that has stymied home building in the US.

Winter storms that shut down petrochemical plants in the Gulf of Mexico have left key products in short supply.

Steep increases in demand made pet food scarce and Grape-Nuts cereal all but disappear from American store shelves for a time.

Some companies were especially exposed to such forces, given that they were already running lean as the crisis began.

And many businesses have combined a dedication to Just In Time with a reliance on suppliers in low-wage countries like China and India, making any disruption to global shipping an immediate problem.

That has amplified the damage when something goes awry - as when an enormous vessel got lodged in the Suez Canal this year, closing the primary channel linking Europe and Asia.

"People adopted that kind of lean mentality, and then they applied it to supply chains with the assumption that they would have low-cost and reliable shipping," said Prof Shih, the Harvard Business School trade expert. "Then, you have some shocks to the system."

In Conshohocken, Pennsylvania, Mr Andrew Romano is literally waiting for his ship to come in. He is vice-president of sales at Van Horn, Metz & Co, which buys chemicals from suppliers around the world and sells them to factories that make paint, ink and other industrial products.

The company could not secure enough of a specialised resin that it sells to manufacturers that make construction materials. The American supplier of the resin was itself lacking one element that it purchases from a petrochemical plant in China. One of Mr Romano's regular customers, a paint manufacturer, was holding off on ordering chemicals because it could not locate enough of the metal cans it uses to ship its finished product.

No pandemic was required to reveal the risks of over-reliance on Just In Time combined with global supply chains. Experts have warned about the consequences for decades.

In 1999, an earthquake shook Taiwan, shutting down computer chip manufacturing. The earthquake and tsunami that shattered Japan in 2011 shut down factories and impeded shipping, generating shortages of auto parts and computer chips. Floods in Thailand the same year decimated production of computer hard drives.

Each disaster prompted talk that companies needed to bolster their inventories and diversify their suppliers. Each time, multinational companies carried on.

Simply expanding warehouses may not provide the fix, said Mr Richard Lebovitz, president of LeanDNA, a supply chain consultant based in Austin, Texas. Product lines are increasingly customised.

"The ability to predict what inventory you should keep is harder and harder," he said.

Ultimately, business is likely to further its embrace of lean for the simple reason that it has yielded profits. "The real question is, 'Are we going to stop chasing low cost as the sole criteria for business judgment?' " said Prof Shih. "I'm sceptical of that. Consumers won't pay for resilience when they are not in crisis."

NYTIMES