US September 2026 CPI: Inflation Rises to 3.7%, Nasdaq Falls 1.9%

U.S. inflation accelerated more than expected in September 2026, triggering a sharp selloff in tech stocks and heightening investor concerns that the Federal Reserve may raise interest rates again.

According to data released by the U.S. Bureau of Labor Statistics (BLS), the Consumer Price Index (CPI) rose 3.7% year-over-year in September, up from 3.4% in August and above the market expectation of 3.6%. Core CPI, which excludes food and energy prices, also came in higher than expected, rising 2.6% year-over-year.

The report, released on October 14, prompted investors to reassess the interest rate outlook. The Nasdaq Composite fell 1.88%, while the S&P 500 dropped 1.11%, with AI infrastructure and semiconductor-related stocks seeing particularly steep declines.

The key question now facing the market is no longer simply whether energy prices are driving up headline inflation, but whether price pressures are spreading across more sectors of the economy, which could prompt the Fed to raise rates again.

Key Takeaways

• September CPI rose 3.7% year-over-year, above the market expectation of 3.6%; core CPI rose 2.6% year-over-year, also exceeding the expected 2.5%.
• The Nasdaq fell 1.88% on October 14, as rising rate hike expectations weighed heavily on AI and tech stocks.
• Market expectations for a Fed rate hike in October increased. According to CME FedWatch, the probability of a rate hike rose to about 37% at the close, up from 22% the previous trading day.

What Did the September 2026 CPI Report Show?

The September CPI report showed that U.S. consumer prices accelerated, with energy prices being the largest contributor to the monthly increase in CPI.

September 2026 CPI Data Overview

• Headline CPI year-over-year: 3.7%, up from 3.4% in August.
• Headline CPI month-over-month: 0.6%, up from 0.4% in August.
• Core CPI year-over-year: 2.6%, up from 2.4% in August.
• Core CPI month-over-month: 0.3%, unchanged from August.

Gasoline prices were the primary driver. The gasoline price index rose 9.1% month-over-month in September and 34.2% year-over-year. The overall energy price index rose 5.2% month-over-month, with the increase in gasoline prices accounting for more than half of the monthly rise in headline CPI.

However, the report also showed that inflationary pressures were not limited to energy:

• Shelter costs: Up 0.4% month-over-month, higher than 0.3% in August.
• Transportation services: Up 0.6% month-over-month.
• Used cars and trucks: Up 0.7% month-over-month.
• Core CPI: Up 0.3% month-over-month, above the market expectation of 0.2%.

Although overall food prices were flat month-over-month, continued increases in shelter and services prices kept the inflation outlook complicated.

This distinction is critical. If oil prices stabilize, a temporary energy price shock may gradually fade. But if core price pressures continue to broaden, inflation could become more difficult to bring under control.

Why Did U.S. Stocks Fall After the CPI Release?

U.S. stocks fell on October 14, primarily because the higher-than-expected inflation data increased the likelihood of further monetary tightening.

The closing performance showed a clear divergence between tech stocks and the broader market.

October 14 U.S. Stock Market Close

• Nasdaq Composite: 26,692.87, down 1.88%.
• S&P 500: 7,718.94, down 1.11%.
• Dow Jones Industrial Average: 51,621.48, down 0.09%.

The Nasdaq posted its largest single-day decline since July 23, while the S&P 500 recorded its biggest one-day drop since July 29.

AI-related stocks saw particularly steep declines. Oracle (ORCL) fell 8.8%, CoreWeave (CRWV) dropped about 15%, and Nebius (NBIS) declined roughly 10%. The Philadelphia Semiconductor Index fell 4.3%.

Rising interest rates can increase the discount rate applied to companies' future expected earnings, thereby compressing growth stock valuations. For companies heavily reliant on borrowing to expand AI infrastructure, financing costs could also rise further.

However, inflation was not the only factor. Company-specific news, including analyst downgrades of Dell and Hewlett Packard Enterprise, also intensified selling pressure on tech stocks.

For investors tracking the Nasdaq 100 through the QQQ ETF, changes in interest rate expectations are also a market signal worth watching. MEXC offers QQQ stock perpetual contracts related to the Nasdaq 100 ETF, whose price performance is linked to the QQQ ETF rather than directly tracking the broader Nasdaq Composite Index.

What Does the September CPI Mean for the Fed's Next Rate Decision?

The September inflation report prompted the market to reassess whether the Fed can hold rates steady at its upcoming meeting.

At its September 16 policy meeting, the Fed raised the benchmark rate target range by 25 basis points to 3.75%–4.00%, emphasizing the need to bring inflation back to its 2% target.

Before the latest CPI release, the market widely expected the Fed to hold rates steady in October.

However, after the data was released, that expectation began to shift. According to CME FedWatch, the probability of another rate hike in October rose from 22% the previous trading day to about 37% at the close on October 14.

This shift reflects a repricing of monetary policy risk, rather than confirmation that the Fed will raise rates.

According to the Fed's official FOMC meeting calendar, the next policy meeting will be held on October 27–28, 2026.

Investors will be closely watching how policymakers interpret the September inflation acceleration: whether it is a temporary energy price shock or more persistent underlying price pressures.

How Will Rising Inflation Affect Stocks, the Dollar, and Other Markets?

The September CPI report once again highlighted the close relationship between above-expectation inflation, interest rate expectations, and stock valuations.

Tech and AI stocks: Rising rate expectations could weigh on valuations of companies highly dependent on long-term earnings growth. Companies that rely on borrowing to fund capital expenditures may face additional pressure.

U.S. Treasury yields: Higher inflation could push up expected policy rates and short-term Treasury yields. Rising yields could also increase the attractiveness of fixed-income assets relative to stocks.

U.S. dollar: Rising U.S. rate expectations typically favor a stronger dollar against other currencies, though geopolitical developments and global growth expectations also influence exchange rate movements.

Energy stocks: Sustained high oil prices could benefit some energy producers, but also increase cost burdens for consumers and energy-intensive businesses.

These effects do not occur equally across all markets or companies. Corporate earnings, balance sheet conditions, and industry-specific events can all lead to divergent market performance.

Investors can track individual company stock performance through MEXC Real U.S. Stocks, and refer to MEXC's educational article on how macroeconomic data affects U.S. stocks to further understand the relationship between inflation, interest rates, and other asset prices.

What Should Investors Watch After the September CPI Release?

Three key upcoming events could determine whether the October 14 U.S. stock selloff was merely a short-term repricing or the beginning of a sustained shift in interest rate expectations.

1. September PPI — October 15

The Producer Price Index (PPI) will provide another signal of upstream inflation pressures in the supply chain. Investors will be watching whether input cost increases have spread beyond energy to other industries.

2. Fed Policy Meeting — October 27–28

The next rate decision will test whether the latest CPI is sufficient to prompt the Fed to raise rates again. Policymakers' comments on core inflation and energy prices may be just as important as the final rate decision.

3. October CPI — November 10

The next consumer price report will show whether the September inflation acceleration has continued. The market will pay particular attention to changes in gasoline, shelter, and core services prices.

The September CPI report sent a clear market signal: inflation rose more than expected, and even excluding food and energy, core price pressures remained elevated.

For U.S. stocks, the key question going forward is whether inflation continues to push market rate expectations higher. This is especially important for AI and tech companies whose valuations and investment plans are highly dependent on the financing environment.