Money Simplified

The Weekly Market Update

12 September to 18 September 2026

Everyone reached for the brake pedal this week.

The Federal Reserve raised American interest rates for the first time in three years to slow inflation, and Japan lifted its rates to the highest level since 1995. The Bank of England held, but only just. And in a stranger twist, the bosses of the biggest AI companies asked for the race to build ever more powerful AI to slow down, which knocked chip shares hard on Monday.

Oil, for once, was the calm one. Saudi Arabia’s back-up pipeline was attacked and the Hormuz talks fell through, yet the price still ended the week slightly lower. The reason why is below.

Markets at a glance

Figures as at the close on Friday 18 September 2026. The Week column is measured from the previous Friday’s close, 11 September 2026. Yearly changes are the 12 month change from Trading Economics, except the mortgage rate, which is Freddie Mac’s year-ago figure. For interest rates and bond yields, both change columns are shown in percentage points, so a move from 4.97% to 5.00% is +0.03 points. A bond yield is simply the yearly return a lender earns for lending money to the government, and it rises when the price of the bond falls. Green means the number went up, red means it went down, whatever that means for your wallet.

01 · Markets & Rates

America raised interest rates for the first time since 2023, and Japan followed two days later

What happened. On Wednesday the Federal Reserve raised its main interest rate by a quarter of a percentage point to a range of 3.75% to 4%. All twelve policymakers voted for it. It is the first increase since July 2023, and it turns the Fed around from a year ago, when it was cutting. Chair Kevin Warsh was blunt: “The plain fact is that inflation is too high and has been for too long.” The Fed’s own projections point to one more rise before the end of the year. On Friday the Bank of Japan raised its rate to 1.25%, the highest since 1995, in a 7 to 2 vote, with Governor Kazuo Ueda saying “our policy phase has changed”. The interest rate on 10 year American government debt topped 5.04% during the week, its highest since 2007, and finished at 5.00%. President Trump, who picked Warsh for the job, wrote on social media that rates should be 1% or lower.

Why it matters. Central banks raise rates to make borrowing dearer and cool spending, which in theory slows price rises. The awkward part is that today’s inflation comes mostly from oil and petrol, which dearer loans cannot fix, so the cost lands first on borrowers. The average American 30 year mortgage rate jumped to 6.95% this week, and credit card and car loan rates track the Fed closely. For Japan, this closes an era in which savers earned almost nothing for three decades. Oddly, the yen weakened after the decision, past 157 to the dollar, because two board members voted against and Ueda gave no hint of a rush to raise again.

What to watch. Kay Haigh of Goldman Sachs expects the Fed to sit out its October meeting because it falls so close to America’s November elections, which would make December the one to watch. Jamie Dimon, the boss of JPMorgan, summed up the mood this week: “It’s not clear to me we’ve slayed inflation.”

02 · AI & Technology

The people building AI asked for it to slow down, and chip shares tumbled

What happened. On Saturday 12 September Dario Amodei, the chief executive of Anthropic, published a 3,900 word essay called “We Must Pace the Frontier”. Its central line: “We must slow the pace at which we improve the capabilities of AI models.” He proposed giving outside safety inspectors permanent, employee-level access inside AI labs, and asked governments to coordinate limits. Within hours Sam Altman of OpenAI replied “I agree with Dario that we need to pace the frontier”, and Elon Musk posted “Dario is right”. Altman also told Fortune that OpenAI will not float on the stock market this year: “given everything happening with safety, right now would be an ill-advised moment to go public.” When trading opened on Monday, the Philadelphia semiconductor index, which tracks the biggest chip makers, closed down 5.9%. Nvidia closed down 3.4%, AMD 4.4%, Broadcom 4.8% and Intel 5.6%. Cybersecurity firms went the other way: CrowdStrike closed up 10.5% and Palo Alto Networks 9%.

Why it matters. The AI boom has been the engine of the American stock market for three years, and it runs on one assumption: that the labs keep buying ever more chips and building ever more data centres. If the labs themselves slow down, so do the orders. That is why the sellers were chip makers and the buyers were security companies, which stand to gain if AI systems need more policing. Kevin Gordon of the Schwab Center for Financial Research warned that a sharper slowdown could have a “recessionary-like impact”. Bank of America’s analysts called the worry “noise” and still expect AI spending to keep surging. By Friday chip shares had clawed back most of Monday’s fall and the sector ended the week close to where it began.

What to watch. Words are cheap and commitments are not. The test is whether the labs actually let outside inspectors in and slow their release schedules, or whether the essay is quietly forgotten. The next round of results from the big chip makers will show whether any orders have changed.

03 · Geopolitics & Energy

Saudi Arabia’s back-up oil pipeline was hit, the Hormuz talks collapsed, and oil still ended the week lower

What happened. On Friday 11 September drones launched from Iraq struck pumping stations on Saudi Arabia’s East-West pipeline, the 1,200 km line that can carry 4 to 5 million barrels a day from the Gulf oilfields to the Red Sea coast without going anywhere near the Strait of Hormuz. Saudi Arabia shut it as a precaution. Since Hormuz closed in March, that pipeline has been the kingdom’s main way out. Then the talks in Oman between Iran, the Gulf states and Iraq on a temporary shipping lane through Hormuz, due on Monday, were postponed with no new date. Iran says Saudi Arabia asked for the delay after objecting to the wording. Brent came close to $110 a barrel on Monday. It then fell for three days running, because Saudi Arabia pushed 2.8 million barrels a day through Hormuz over six days, against just 700,000 a day in August, and Aramco said it expects to restore about half the pipeline’s flow within days and all of it within about six weeks. Brent settled at $103.87 on Friday, down 0.7% on the week.

Why it matters. Every buffer that has kept the world supplied for six months is now damaged or in dispute. Analyst Ben Cahill put it this way: “The key buffers that got us through the last six months have basically been worn away.” American diesel hit a record $6.29 a gallon this week, and diesel is what moves lorries, trains and farm machinery, so it works its way into the price of almost everything. Haris Khurshid of Karobaar Capital: “I wouldn’t call it an all-clear situation. The market is getting some capacity back, but it isn’t getting its margin for error back.”

What to watch. President Trump meets Gulf leaders in New York on Tuesday 22 September, on the sidelines of the United Nations General Assembly, and said this week that “we could have a deal any time we want”. Watch the pipeline restart and the daily count of ships through Hormuz. Both matter more for your petrol bill than anything a central bank does.

04 · Business & Economy

UK inflation rose to 3.1%, and three of the Bank of England’s nine policymakers wanted a rate rise

What happened. Prices in Britain were 3.1% higher in August than a year earlier, up from 2.9% in July and the highest since March, the Office for National Statistics said on Wednesday. Transport costs rose 4.6%, driven by petrol, with dearer air fares adding to it. The core rate, which leaves out food and energy, stayed at 2.6%. On Thursday the Bank of England kept Bank Rate at 3.75%, but the vote was 6 to 3, with Megan Greene, Catherine Mann and Huw Pill all wanting 4%. The Bank now expects inflation to reach about 3.75% by the end of this year and go slightly above 4% in early 2027 before it eases. Since July, Brent crude has risen 36% and the wholesale price of gas in Britain 78%.

Why it matters. Britain has the same problem as America, only more so, because it imports its gas. The energy price cap rises 4% in October to £1,723 a year for a typical household, and Cornwall Insight, which forecasts the cap, expects a further rise to about £1,872 in January. The Bank said there is “little evidence so far of material second-round effects”, meaning wages and shop prices have not yet started chasing energy higher, and that is exactly what it is watching for. It also said the risks are “tilted to the upside”. Three votes for a rise is a sign that patience is running short.

What to watch. The Bank next decides on 5 November. Two more members switching sides would mean a rise, and the September inflation figure in the middle of October is the number most likely to move them. The Bank also confirmed it will keep selling the government bonds it bought during past crises, about £46 billion a year until 2034, which quietly adds to the pressure on borrowing costs.

05 · Personal Finance

Mortgage rates jumped on both sides of the Atlantic, and most savings accounts still pay less than inflation

What happened. In America the average 30 year fixed mortgage rate rose to 6.95% this week from 6.76%, according to Freddie Mac, its highest since January and up from 6.26% a year ago. In Britain, Moneyfacts says the average two year fixed deal has climbed from 5.63% in early August to 5.73% by the middle of September, and the average five year fix from 5.66% to 5.78%. NatWest, Santander, HSBC and TSB have each raised prices twice in a month. Savers are not getting the other side of the bargain: the big high street banks pay an average of just 1.16% on easy access accounts, far below 3.1% inflation, although more than 190 accounts on the market do beat inflation and the best pay 4% or more.

Why it matters. A fixed mortgage rate is a bet on where interest rates will be over the next two or five years, not where they are today, so deals moved before Thursday’s hold and would have moved even if the Bank had sat still for months. Rachel Springall of Moneyfacts: “The mortgage pain shows no sign of easing for borrowers unable to lock in new deals.” For savers the gap is the story. Moneyfacts estimates about £300 billion is sitting in accounts paying no interest at all, and that moving it to a 4% account would earn savers roughly £12 billion a year between them.

What to watch. Many lenders let borrowers reserve a new rate months before a deal ends, so the people most exposed are those whose fixes end in the next year and have not yet looked. Oliver Dack of Mortgage Advice Bureau: “putting off finding a mortgage will likely only add to frustrations.” For savings, the simple check is whether the rate you are actually getting is above 3.1%. If it is not, your money is shrinking in real terms.

Also worth knowing

Trump signed a law allowing 100% tariffs on the biggest buyers of Russian oil. On Friday the president signed the Graham Act, which lets him put tariffs of up to 100% on goods from the five largest purchasers of Russian oil and gas. China buys about half of Russia’s crude exports and India about 37%, and both have said they will protect their interests. It is a power to use rather than an automatic tariff, so the question is whether he uses it.

Bitcoin climbed back above $80,000. It closed the week around $81,100, up about 6% on Friday alone and 5.2% on the week, after America’s derivatives regulator sent two sets of crypto rules to the White House following the failure of the CLARITY Act in the Senate. Traders read that as regulation moving ahead even without a new law. It is still roughly 36% below its record of about $126,000 set last October.

Apple’s iPhone 18 Pro went on sale on Friday, with queues outside stores from London to New Jersey. The Pro starts at $1,199, the Pro Max at $1,299 and the folding iPhone Duo at $1,999. The headline feature is a new Siri that runs on Google’s Gemini models and can read your messages, photos and emails to draft replies and edit pictures. The cheaper standard iPhone 18 does not arrive until the spring.

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This newsletter is for educational purposes only and does not constitute financial advice. Figures as at the close on 18 September 2026.