[September 2026] Stock Market Summary | Japan, US, and Europe all raise interest rates, yet AI stocks remain strong
In this article, we look back at the stock market in September 2026.
In September, as concerns about inflation persisted due to rising oil prices caused by the situation in the Middle East, the ECB, the Fed, and the Bank of Japan all raised interest rates.
Long-term interest rates rose globally, creating a headwind for the stock market, but expectations for AI and semiconductor-related sectors remained strong, leading to gains in the NASDAQ and Taiwanese stocks.
It was a month where, even within the same category of “stocks,” there was a significant divergence depending on the country, index, and industry.
In this article, we will organize the following points in order:
* How did Japanese stocks move?
* What drove the market domestically?
* Which markets were strong globally?
* Why did interest rates rise globally?
* What should we pay attention to in October?
We will break down these points one by one.
1. Domestic stock price movements
Nikkei Stock Average rises, TOPIX falls
Index September PerformanceNikkei 225 +0.67%TOPIX -1.15%
In September, the Nikkei Stock Average rose slightly, while the TOPIX fell.
At first glance, it might seem that “Japanese stocks were not that bad,” but looking at the market as a whole reveals a slightly different picture.
So, why was there a difference between the Nikkei and the TOPIX?
The Nikkei is a price-weighted index consisting of 225 stocks, and it has the characteristic of being easily influenced by the price movements of a few high-priced stocks.
In September, some high-priced stocks, such as those related to semiconductors, rose.
③ Global stock market movements
Next is global stocks.
First, let’s check the overall trend using four ETFs.
* VT = Global stocks overall
* VTI = US stocks
* VEA = Developed markets excluding the US
* VWO = Emerging markets
September ETF performance
Target ETF September performance
US VTI -1.03%
Global VT -1.68%
Emerging markets VWO -2.00%
Developed markets ex-US VEA -3.17%
* Comparison based on US dollar-denominated Price Return.
All four fell in September.
However, there was a significant difference depending on the region,
US > Global > Emerging markets > Developed markets ex-US
was the order.
While the decline in US stocks was relatively small, developed markets outside the US and emerging markets fell more significantly.
Even greater differences by country/region
Country/Region Representative Index September performance
Taiwan Taiwan Weighted +3.93%
South Korea KOSPI +0.26%
US S&P 500 -0.45%
Japan TOPIX -1.15%
Europe STOXX 600 approx. -2.5%
Australia ASX 200 -3.16%
China Shanghai Composite approx. -3.6%
Hong Kong Hang Seng approx. -3.7%
India Nifty 50 -6.06%
Indonesia IDX Composite -6.96%
* Comparison based on local currency-denominated Price Return for representative stock indices of each country/region.
In September, Taiwan was the strongest at **+3.93%**, and South Korea also rose, albeit slightly.
Meanwhile, the US, Japan, and Europe declined.
In addition to China and Hong Kong, India and Indonesia also fell significantly.
It was a month with such large regional differences that it cannot be summarized simply by saying “global stocks fell.”
Even so, AI and semiconductor stocks were strong
While the global stock market was sluggish, the strength of AI and semiconductor-related stocks stood out.
In the US in particular, there was a significant gap between the three major indices.
Index September performance
NASDAQ +1.86%
S&P 500 -0.45%
NY Dow -4.29%
While the NASDAQ rose, the S&P 500 fell slightly, and the NY Dow fell by more than 4%.
Expectations for capital investment in AI-related fields and demand for semiconductors supported large-cap technology stocks.
On September 22, the NASDAQ hit a new closing high.
Also, Taiwan, which was the strongest by country/region, was **+3.93%**.
The presence of semiconductor-related companies in the Taiwanese market is significant, and expectations for AI and semiconductor demand became an important factor supporting the stock market.
In other words, September was a month where, despite the headwind of rising global interest rates, the strength of growth expectations for AI and semiconductor-related fields continued.
④ Major global topics
Next, we will look at the major global topics in September.
Particularly important were:
* Escalation of the Middle East situation and rising oil prices
* Interest rate hikes by the ECB and FRB
* Rise in US long-term interest rates
* Trends in the US economy and inflation
is what they are.
Oil prices rose due to the escalation of the Middle East situation
One of the important themes in September was crude oil.
Concerns about oil supply and transportation increased due to the escalation of the Middle East situation, and Saudi Arabia’s East-West pipeline was also temporarily suspended.
Supply anxiety became a factor pushing up oil prices, and Brent crude oil rose by about 14% in September.
The November contract, which matured on September 30, was $103.50. Meanwhile, the December contract, which had become the main one, closed at $98.03.
When oil prices rise, it can affect prices through gasoline, transportation costs, manufacturing costs, etc.
Therefore, in September, vigilance against inflation due to high oil prices also became an important theme for the market.
ECB and FRB also raise interest rates
In September, interest rates were raised not only in Japan but also in Europe and the US.
September 10 ECB: 0.25% rate hike -> 2.50%
September 16 FRB: 0.25% rate hike -> 3.75-4.00%
September 18 Bank of Japan: 0.25% rate hike -> 1.25%
Major central banks in Japan, the US, and Europe all raised policy interest rates in the same month.
In the US, this is the first rate hike in about three years.
It was shown once again that responding to inflation remains an important issue for major central banks.
US long-term interest rates at their highest level since 2002
In addition to interest rate hikes,
* Persistent inflation
* Resilience of the US economy
* Vigilance regarding fiscal and government bond supply and demand
also overlapped, and US long-term interest rates rose significantly.
The US 10-year Treasury yield rose to around 5.3% at the end of the month.
The 30-year Treasury yield also rose to the 5.6% range.
Rising interest rates not only increase corporate financing costs but also act as a headwind for stock valuations.
The US economy maintains resilience
August retail sales were +1.2% month-on-month.
Furthermore, the final GDP figure for the April-June quarter was revised upward to **+2.2% annualized**.
The resilience of the economy is a positive factor for corporate performance.
On the other hand,
The economy is strong
↓
Demand is hard to fall
↓
Inflation is also hard to fall
↓
Possibility of prolonged high interest rates
There is also this aspect.
It is a phase where one cannot simply think “a strong economy = always positive for stocks.”
Signs of slowing inflation at the end of the month
The August PCE price index was **+3.4% year-on-year**, which was lower than the market forecast of +3.7%.
Following this, expectations for an additional rate hike at the October FOMC fell to just under 40%.
However, this figure also includes the impact of the BEA’s change in the calculation method for some service prices.
Therefore, one should not judge that inflation has slowed significantly based on this figure alone, and it is necessary to check future data as well.
On the other hand, due to the resilience of the US economy, long-term interest rates ended September at a high level.
Inflation re-accelerates in Europe
Europe’s STOXX 600 fell about 2.5% in September.
It was the first monthly decline in six months.
Germany’s September inflation rate also accelerated to **3.3%** in the preliminary report.
Vigilance against inflation and high interest rates continues in Europe as well.
Gold prices also fell
The spot gold price fell about 6.6% in September.
Since gold does not have cash flows like stock dividends or bond interest, its relative attractiveness tends to decrease when government bond yields rise.
In September,
Oil ↑
Long-term interest rates ↑
Gold ↓
The movement between assets was also characteristic.
⑤ Points to watch in October
From here on, we will look at the points to watch in the future, including information known as of October 4.
1. US employment falls below expectations; next up are CPI and FOMC
In the US employment report for September released on October 2, non-farm payrolls increased by only 29,000 from the previous month, significantly below the market expectation of 90,000. The unemployment rate was 4.2%.
With employment growth falling well below expectations, expectations for an additional rate hike at the October FOMC have receded to the 20% range.
Moving forward, attention will be on what decisions the Fed makes at the October 27-28 FOMC, while confirming data such as the CPI on October 14.
2. Crude oil prices and the Middle East situation
Brent crude oil rose by approximately 14% in September.
If high crude oil prices persist, they could impact monetary policy through prices.
Conversely, if supply concerns ease and crude oil prices fall, it could lead to a retreat in inflation concerns.
3. The Bank of Japan’s next move
The Bank of Japan raised interest rates in June and September.
The focus will now be on the timing of additional rate hikes while confirming prices, wages, and corporate inflation expectations.
Attention is also on Japan’s long-term interest rates, which have risen to the 3% range, in addition to the policy rate.
4. Corporate earnings and AI investment
Despite the headwind of rising interest rates, AI-related stocks showed strength in September.
Micron announced its earnings after the US market closed on September 30.
Revenue was $54.23 billion, and the revenue forecast for the next quarter was $61.5 billion ± $1.5 billion, exceeding market expectations.
This is backed by strong demand for memory for AI data centers.
From October onwards, it will be important to confirm through corporate earnings not just ‘expectations for AI,’ but whether AI investment is leading to actual sales and profits.
6. Summary
If I were to describe September in one phrase, I would say it was:
‘A month where growth expectations for AI and semiconductors supported parts of the stock market while inflation and rising interest rates shook the market.’
Crude oil prices rose due to the escalating situation in the Middle East, strengthening vigilance against inflation.
And with inflation remaining high, the ECB, Fed, and Bank of Japan all raised interest rates.
Long-term interest rates rose globally, creating a headwind for the stock market.
Even so, the NASDAQ and Taiwanese stocks rose, confirming the strength of growth expectations for AI and semiconductors.
In the Japanese market, the Nikkei Stock Average rose slightly, while the TOPIX fell, showing a divergence depending on the index.
On the other hand, year-to-date, non-ferrous metals, banks, shipping, and electrical appliances are among the top performers, and themes symbolizing 2026—such as AI/data centers, rising interest rates, and geopolitical risks—are reflected in stock prices by sector.
In other words, September was a month where investors’ experiences differed greatly depending on ‘which country, which sector, and which stocks they held,’ rather than just looking at the indices.
In October, I would like to focus on these two trends: ‘crude oil, inflation, and interest rates’ and ‘growth in corporate profits centered on AI.’
—
Reference
Bank of Japan, FRB (Federal Reserve Board), ECB (European Central Bank), JPX (Japan Exchange Group), US government statistics, Reuters, market data for various stock indices and ETFs, etc.
*Stock prices, indices, interest rates, etc., are generally as of the end of September 2026. Monthly performance is calculated from the last trading day of August to the last trading day of September, and year-to-date performance is calculated based on Price Return from December 30, 2025, to September 30, 2026. Only section 5 reflects information published as of October 4.