One is a weighted list of a hundred share prices. The other is what happens in British workplaces and shops. The evening bulletin reads them out together.
The index was assembled to be traded, not to describe a country
Four numbers about Britain arrive together most evenings: growth, inflation, the pound and the FTSE 100. Three are attempts to measure the place. The fourth is the capitalisation-weighted price of a hundred companies listed on one exchange, ranked by what they are worth rather than by where they operate. The running order does the arguing.
The ranking rule is the whole of it. Membership follows market value, and market value is set by whoever is buying, which includes sovereign funds, trackers in Ohio and hedging desks with no British customers whatever. Nobody assembling the index was building a national scoreboard. They were building something a futures contract could settle against, a different brief with different virtues.
Read down the constituent list and the pattern is hard to miss. Oil majors, miners with no British pit, banks whose profit centres sit in Asia, pharmaceutical firms selling into American healthcare, consumer goods businesses growing in emerging markets. A large share of what this index earns is earned somewhere else, invoiced in somebody else’s currency.
The weighting rule pushes in the same direction as the geography. Companies reach the largest market values by outgrowing a single country, so the constituents carrying the most weight tend to be the least domestic. Two independent mechanisms, one outcome. That much is structural. How big the effect is turns out to be far harder, and this article returns to it.
Two prices Britain does not set
Profit earned in dollars is reported in pounds, so a translation happens before any figure reaches an investor. Sterling weakens, the same overseas profit converts into more pounds, and reported earnings rise without one extra unit being sold. Nothing about British output moved. A measuring stick did, and a moving stick is easily mistaken for news about the thing measured.
Then look at what sets the stick. Sterling accounts for 10.2% of global foreign exchange trades on the Bank for International Settlements Triennial Survey for 2025, a heavily traded currency argued over by people with no stake in a British high street. So an index revaluing on the pound takes its second reading from a market that is itself global.
The resources constituents make the point without any translation. What an oil major or a copper miner earns is a function of a benchmark quoted in dollars and set by global supply against global demand, where the marginal buyer is likelier to be in Shanghai than in Sheffield. British weather, wages and confidence do not enter that calculation. Which produces the reading that turns up whenever the country has a difficult quarter. Resources weight can lift the index in a flat month and weigh on it in a healthy one, and neither movement is a verdict on anything happening here. National accounting was never the job.
| What the index responds to | Where that input is priced | How much of it Britain decides | Does it move a household the same way? |
| Sterling against the dollar | A continuous global market | Some, through rates, gilts and politics | Usually the opposite way, and quickly |
| Oil, gas and metal benchmarks | Global exchanges, in dollars | Very little | Often opposed, since somebody’s revenue is somebody’s bill |
| Global rate expectations | Bond markets, mostly abroad | Partly, through the Bank’s own rate | The same way, and for the same reason |
| British consumer demand | Here, in shops and on payslips | Nearly all of it | The same way, on the minority that sells here |
| Tax and listing rules | Westminster and the exchange | All of it | Slowly, and mainly through where firms choose to list |
| Who is in the index at all | The quarterly review, on market value | An arithmetic outcome rather than a British decision | Not at all, which is the point |
Six inputs the index responds to, where each one is priced, and whether a British household feels it the same way.
A hundred listed companies is a narrow window on any country
Set the geography aside for a section, because the coverage problem survives without it. Everything in this index is listed, and listing is a financing choice rather than an economic category. The businesses that never listed, the partnerships, the mutuals, the family firms, the whole public sector and the several million people working for themselves are outside it by construction, and a great deal of British employment sits in that outside.
So a hundred companies selling only to British customers would still be a reading of the listed corner rather than of the place, and the list stops at a hundred, which narrows the window again to the largest end of that corner.
No failure is being described. The thing was specified as a tradable reference, and such a reference has to be short enough to hedge and liquid enough to settle against, which are poor criteria for a census and the right ones for a contract.
Britain is in there, it is just not where people look for it
This argument is now old enough to be used lazily. It gets deployed as though index and country were strangers, which is plainly false. These companies employ British staff, pay British corporation tax, answer to British regulators, sit inside British pension funds and trade under British listing rules. Several, the banks, the utilities, the supermarkets, take most of their money from British customers.
One channel runs through every name regardless. The Bank of England’s rate and the gilt curve set the discount rate against which all of them are valued, foreign earnings included, so a domestic monetary decision reaches an index of global businesses inside the hour. The defensible version of the claim is about weight, not connection. A poor proxy is a long way from no proxy.
This article stops short of a percentage on purpose
Notice what has not appeared above. The natural next sentence puts a number on the overseas share of FTSE 100 revenue, usually to two significant figures and with no year attached. There is no revenue-by-geography breakdown behind this one, so the claim stops at large and declines to proceed to seventy-something. The restraint earns its place, because that number is slippery. It moves with the year chosen, with whether you weight by revenue or by market value, with whether a bank’s booking centre counts as where the money was made, and with a firm reporting two segments where its rival reports nine. Anyone offering a single figure should be able to name all four choices.
One half of this decision has a bill attached
Split the question in two. What a FTSE position costs can be settled by opening one and paying: the spread crossed twice, the financing charged for every night it survives, the conversion where the account currency differs. None of that reads off a fee schedule, which is the argument for the way The Investors Centre works, funding live accounts with its own money to test UK trading platforms rather than compiling rankings from providers’ published fee schedules.
The limit of that lands on this article’s question. A funded account produces an accurate bill, and an accurate bill is silent about what you have bought exposure to. Testing the platform prices the toll. It says nothing about whether the road goes where you assumed, and a method built to catch charges will keep catching them on a position whose premise was wrong all along.
Which Britain did you mean?
The useful question therefore arrives before any platform comparison. If the reason for wanting exposure to this index is a view about British households, wages or domestic demand, then an instrument weighted toward companies that outgrew all three is a strange way to express it. The mismatch never announces itself. It shows up as a position moving for reasons unconnected to the argument made for holding it.
If the reason is a view about commodities, the dollar and the pound, the same index may fit the thought precisely and the domestic story is scenery.
Either way the premise is worth writing down before the ticket is opened, because the cost of holding it is the only part anybody will quote you an exact number for. Everything else has to be argued.
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