Nasdaq Hits Record High! Looking Back at the U.S. Stock Market on September 21 as Oil and Interest Rates Take a Breather｜nisalaryman1993

This morning, I opened my brokerage app with a cup of coffee in hand and let out an involuntary “Oh.” Last week, I had been sighing every time I looked at my account balance due to rising oil prices and interest rates.

I imagine many of you are wondering, “Last week was tough, but how was yesterday?” In this article, I will gently break down what happened in the U.S. stock market on Monday, September 21, 2026 by separating the numbers from the context.

Thumbnail

Yesterday’s U.S. stock market saw a “broad-based rally”

All three major indices rose together

Let’s start with the results. According to the Associated Press, the closing prices for the major indices are as follows:

• S&P 500: +1.49% (+114.20 pts) at 7,764.70. Just 0.4% away from a record high.

• Dow Jones Industrial Average: +0.71% (+$366.19) at $52,048.83

• Nasdaq Composite: +2.26% (+599.55 pts) at 27,122.09. Highest level since June

• Russell 2000 (Small-cap stocks): +0.5% at 2,875.36

The Nasdaq saw particularly large gains, making it a day led by tech stocks.

A tailwind for global stock markets as well

The rise wasn’t limited to the U.S. Stock prices in various countries, including Germany, Hong Kong (+1.2%), and South Korea (+1.6%), also rose by over 1%, while France was up +0.9%. It can be said that it was a day when the appetite for “taking risks” returned globally.

How should we interpret these numbers?

A +1.49% gain for the S&P 500 is quite significant for a single day’s movement. It means the index jumped from the 7,650-point range at the previous day’s close back into the high 7,700s.

For those of us who are steadily investing in S&P 500 or All-Country (eMAXIS Slim) mutual funds, it must have felt like a day where “a good portion of last week’s losses were recovered.”

However, the small-cap Russell 2000 only rose by +0.5%. Compared to the gains in large-cap tech stocks, this was modest, and it seems more accurate to view it as “large-cap tech stocks pushing up the indices” rather than “a wide range of stocks being bought simultaneously.”

The reasons for the rise: “A breather in oil and interest rates” and “semiconductors”

Diagram 1: The flow of the stock market rise on September 21

Crude oil and long-term interest rates both fall

Last week, the market was shaken by rising oil prices and interest rates. Yesterday, both of those factors calmed down.

• Brent crude: -3.4% to about $100.3 (it rose to about $110 last week)

• WTI crude: -4.51% to $95.78

• U.S. 10-year Treasury yield: Fell from 5.01% on Friday to around 4.96%

When oil prices fall, concerns about corporate costs and inflation ease, and when interest rates fall, the sense that stocks are overvalued diminishes. For high-tech stocks, where expectations for future growth are concentrated, falling interest rates are particularly likely to act as a tailwind.

On the other hand, gasoline prices are still at a fairly high level, averaging $4.48 per gallon nationwide, compared to $3.18 a year ago. The burden on household budgets is likely to continue for a while.

AI and semiconductor stocks take center stage

The most notable movement yesterday was the significant rise in semiconductor stocks.

• Intel: +12% to $121.78. Highest price since July

• AMD: About +10% to reach the $600 range for the first time, hitting a market capitalization of $1 trillion

• Arm: Over +15%

• Nvidia: +2.3%

The background to this is the expectation for “AI agents.” As AI begins to handle multi-step tasks on its own, the role of CPUs in planning and executing processes increases. It is believed that the AI market, which has been dominated by GPUs, is now expanding to include CPU manufacturers.

Furthermore, Meta rose +11.4%. In addition to its AI agent “Muse” becoming the top download on the Apple App Store, expectations have risen ahead of the company’s developer conference, “Connect,” on September 23-24.

Also, with Bitcoin hitting its highest level since January, crypto-related stocks such as Coinbase (+4.8%) and Robinhood (+4.2%) also rose.

Three points of caution that prevent unreserved celebration

Diagram 2: Comparison of positive factors and cautionary factors

Yields around 5% and vigilance regarding inflation

While it was a good day, there are also some voices of concern.

• Morgan Stanley warned that if energy prices rise further and the 10-year Treasury yield remains near 5%, the S&P 500 could fall by 7%.

• Chicago Fed President Goolsbee noted that inflation may have shifted to being demand-driven, stating that faster interest rate hikes might be necessary.

• US Treasury yields had recently risen to their highest level in about 20 years.

In other words, yesterday’s gains were largely due to the fact that “interest rates fell slightly,” and if rates rise again, they could easily reverse. In fact, the gains were centered on technology and communications, while energy stocks fell. Gold was also sold off, down -0.93% to $4,383.90.

Data suggesting “September is weak”

I would also like to introduce another piece of seasonal data. According to Investrade, the S&P 500 was down month-to-date as of the 13th trading day of September this year. Since 1950, this situation has occurred 34 times, and it has returned to positive territory by the end of the month only once.

Of course, past patterns do not necessarily apply to this year. Even so, it might be a bit early to conclude that “the trend has completely changed due to one day of significant gains.”

Key events to watch this week

This week, there are a series of scheduled events that could move the market.

• US-China Summit: President Xi Jinping will visit the US from September 23-25. Trade, tariffs, Taiwan, and AI are on the agenda.

• UN General Assembly: Discussions related to Iran. The situation in the Middle East and the Strait of Hormuz are directly linked to oil prices.

• Meta Connect (September 23-24), and McDonald’s Investor Day (Wednesday).

Summary

• On September 21, the three major indices all rose. The Nasdaq hit its highest level since June, and the S&P 500 was within 0.4% of its record high.

• The reasons for the rise were a breather in oil prices and long-term interest rates, and significant gains in AI and semiconductor stocks

• Large-cap tech stocks were the stars, with Intel up 12%, AMD reaching a $1 trillion market cap, and Meta up 11.4%.

• However, yields near 5% and inflation concerns remain, and energy stocks fell.

• This week, focus on the U.S.-China summit and the movement of crude oil.

It is recommended that you do not get caught up in the daily price fluctuations and instead just keep an eye on the news regarding this week’s U.S.-China summit.