Receive free UK economy updates

We’ll send you a myFT Daily Digest email rounding up the latest UK economy news every morning.

It was almost nine years ago to the day when the question of where Britain would rank among the US states for economic heft first became “a thing”. In an article for the Spectator, Fraser Nelson calculated that on a gross domestic product per capita basis, and after adjusting for price differences, the UK would sit in 49th place out of the 50 US states, narrowly squeezing in ahead of Mississippi.

As Britain’s economy has half slumbered, half stumbled its way through the nine years since, pausing to commit occasional acts of egregious self-sabotage, the Mississippi Question has only grown more popular. Could this be the year the UK economy is surpassed by that of the US state with America’s highest poverty rate and a life expectancy almost 10 years shorter than Britain’s?

For a fleeting moment recently, it looked like the time had come, but this was due to an erroneous comparison of nominal figures for Mississippi with inflation-adjusted numbers for the UK.

So no, the short answer is that to date, Britain remains free of that one particular ignominy. GDP per capita has remained ahead of Mississippi’s by about 15 per cent over the past two decades, and indeed as recently as 2019 the UK ranked ahead of no fewer than six of America’s poorest and most economically anaemic states. Heady days, indeed.

But the focus on one comparison, and one surface-level statistic, masks more interesting — and no less troubling — trends beneath the surface. If we’re going to compare Britain to each of the US states individually, then why not also look at the UK’s constituent parts?

It will surprise nobody that London accounts for an outsized share of Britain’s output, but the magnitude of the UK’s economic monopolarity is remarkable. Removing London’s output and headcount would shave 14 per cent off British living standards, precisely enough to slip behind the last of the US states. Britain in the aggregate may not be as poor as Mississippi, but absent its outlier capital it would be.

By comparison, amputating Amsterdam from the Netherlands would shave off 5 per cent, and removing Germany’s most productive city (Munich) would only shave off 1 per cent. Most strikingly, for all of San Francisco’s opulent output, if the whole of the bay area from the Golden Gate to Cupertino seceded tomorrow, US GDP per capita would only dip by 4 per cent.

Britons have mixed feelings about London. It’s the home of the metropolitan elite and sometimes seems more at home with New York than Newcastle, but it keeps Britain economically afloat. Not only in terms of the goods and services it produces but also in its higher tax revenues and fiscal transfers to poorer parts of the country.

There were fears that the capital would suffer more from Brexit than most regions, but thus far the opposite has been true. Exports of services have held up relatively well while trade in goods has cratered, and London’s economy is 4 per cent larger today than it was in 2019, bucking the broader national trend of stagnation or decline. London is the only one of the 10 regions in England and Wales to have grown in every quarter since the nadir of the pandemic recession in the second quarter of 2020, while three others — including the South East — have dipped into regional recessions in the past 12 months.

This is not to say the capital is in rude health — its status as the pre-eminent global financial hub is slipping away, and its productivity growth has been lagging behind that of the rest of the country for the past 15 years — but merely to highlight the double-edged sword Britain has ended up with.

Its capital is the one thing keeping the UK hanging on in the upper economic echelons, but the decades-long London-centricism of everything from finance and culture to politics has engendered a reluctance to allow any other part of the country to be an agent in its own destiny in the way that London has been.

If Britain is to one day banish the Mississippi Question and return to upward mobility, it will require more than one economic engine.

john.burn-murdoch@ft.com, @jburnmurdoch