Under normal circumstances, this just-in-time system is convenient. Yet it is also, as we have discovered in the past fortnight, fragile.

This month, the government advised those with coronavirus symptoms to spend seven days at home “self-isolating.” Like many others, I read this advice, looked in my fridge, and thought, Yikes. My subsequent trip to the supermarket wasn’t evidence of hoarding; it was proof that I had been running an overly efficient supply chain into my own home. Changed circumstances meant I had to change my behavior.

Unfortunately for us all, so did many others. “Temporary shortages are being caused by people adding just a few extra items and shopping more often,” said Fraser McKevitt, the head of retail and consumer insight at Kantar, which monitors consumer spending. The company’s study of 100,000 British shoppers found that only 6 percent of those buying liquid soap, and only 3 percent of those buying pasta, “have taken home extraordinary quantities.”

Yet that relatively small, unexpected surge in demand was enough to generate social-media snapshots of bare shelves at inner-city supermarkets. When amplified by the traditional media, those frightening pictures convinced more of us that there was a problem with food supply. And, like in a bank run, perception quickly became reality. Big queues started to form. Online slots for supermarket deliveries filled up. The situation spiraled.

What happened at supermarkets is worth dwelling on, because it reveals a problem with one of the modern world’s most hallowed concepts: efficiency. As businesses and governments chase ever-tighter margins—ever-greater efficiency—they have created systems that are finely tuned, but also delicate. Many of us are individually guilty of indulging this tendency, encouraged by the trendsetters of Silicon Valley. “The tech sector’s overarching philosophy remains bent towards treating the human brain and body like a machine that can be tweaked and perfected until it is running at peak efficiency,” the journalist Lux Alptraum wrote for Quartz in 2017. This is, however, a fundamentally inhuman philosophy. People aren’t machines. We are inherently inefficient, with our elderly parents and sick children, our mental-health problems, our chronic diseases, and our need to sleep and eat. And, as the past few months have demonstrated, our susceptibility to novel viruses.

We have been trained to see efficiency as a desirable goal. We often don’t see, or don’t acknowledge, the risk of catastrophic meltdown. Think of efficiency as a high-performance engine. Under perfect conditions, it delivers maximum power and minimum waste. However, that very efficiency makes it less robust. Highly efficient systems have no slack, no redundancy, and therefore no resilience and no spare capacity. That’s a problem because perfect conditions rarely exist for long in the real world, and “rare” events happen more often than you’d think. (Climate change, for example, has turned “once in a century” challenges such as extreme heat waves and floods into more regular occurrences.)