How efficiently could you make a sandwich? No, I’m not talking about just wedging ham and cheese between slices of bread. I mean: how cost-effectively could you produce a sandwich entirely from scratch?

In 2015 a YouTuber called Andy George took on just that challenge. He built a garden to grow vegetables and undertook thermal distillation of seawater he’d collected to obtain salt to pickle them. He milked a cow for cheese. He grew, separated and ground wheat for bread, and he pressed sunflower seeds to create his own mayonnaise. As for the protein, he slaughtered, plucked and cooked a chicken.

The result was a prime lesson in economics: doing it yourself, or “self-sufficiency”, turned out to be a costly and time-consuming affair. Despite using tools made by others, it cost George more than £1,500 (in 2023 prices) and six months to make a disappointing chicken sandwich that would have cost perhaps a fiver at a café.

Despite these obvious benefits of specialisation and trade, Britain’s national conservatives contend that national self-sufficiency breeds economic “resilience”. Danny Kruger, an MP, advocates for self-reliance in “food, energy and other critical industries”, while Nick Timothy, Theresa May’s former chief of staff, wants governments to bolster domestic manufacturing.

The nat cons say we should chuck money at sectors such as semiconductors and green energy because the age demands extra capacity (“just in case”) rather than relying on pesky foreigners’ on-demand production (“just in time”). The gist? Covid and supply-chain woes apparently showed the virtues of governments supporting domestic production and spare capacity, even at the expense of efficiency.

It’s true, recent years have seen many firms reconsider brittle supply chains and the political risks of their sources. Yes, there are some national defence outputs governments must protect. But the nat cons’ over-reach in generalising a trade-off between “efficiency” and “resilience”. Following through on the logic would leave us poorer and more vulnerable.

Why? Market specialisation and open trade, by diverting people towards productive activities, makes us richer, which produces billions for relief efforts when crises hit. This is not a frill, it’s a necessity. Setting aside tonnes of capacity to produce stuff required primarily during once-in-a-century events would require either huge amounts of wasted resources in normal times or eternal gluts of products. Costs would be vast.

Domestic shocks occur too: think BSE, foot-and-mouth disease or Covid outbreaks. Free trade with many nations reduces exposure to these and helps diversify supplies as insurance against disruption. Ask new American mothers: the US used protectionism, regulation and government contracts to sow up the baby formula market for domestic suppliers — delivering “self-sufficiency”. Then a factory was shuttered unexpectedly, producing shortages everywhere.

Many nevertheless think “self-sufficiency” as prudent insurance for extreme scenarios such as trade blockades. Yet even in the First World War, our “dependence” on imported food enhanced our resilience. Importing Argentinian beef and Danish bacon freed workers for munitions production, while farmer-heavy Germany struggled to mobilise. Worries about a potential China-Taiwan conflict disrupting trade and semiconductor production are today understandable, but why reshore, rather than deepening trade with friendly allies?

Given no government can accurately predict future shocks, claims that reshoring insulates us from interdiction or disruption are therefore, at best, speculative. What we know for sure is the parable of the sandwich: junking specialisation for self-sufficiency comes with a high cost.