The AI boom has triggered one of the costliest building sprees in history. Over the past three years, leading tech firms have committed more capital expenditure toward AI data centres, chips and energy than the United States spent building the entire interstate highway system over four decades, even adjusted for inflation. Unlike highways, however, no one can say what these investments will do for global productivity.

Are the colossal sums being poured into artificial intelligence (AI) a ruinous waste of money, or an investment that will transform the world?

Few doubt the technology's potential. The real question is whether the spending that the technology requires is economically viable. On this point, there is no more important question facing the global economy today, such is the dependence that global growth has on a financially and economically feasible future for AI.

The AI boom has triggered one of the costliest building sprees in history. Over the past three years, leading tech firms have committed more capital expenditure toward AI data centres, chips and energy than the United States spent building the entire interstate highway system over four decades, even adjusted for inflation.

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Unlike highways, however, no one can say what these investments will do for global productivity. Moreover, no one knows when, or even if, the companies funding the investments will earn their money back.

What does this spend look like?

This year alone, America's "hyperscalers" (to use the ghastly lexicon) -- Amazon, Google, Meta and Microsoft -- have pledged to spend a record R5.5-trillion ($320-billion) on capital expenditures (capex), much of it on building massive data centres...