Which major index lost 4.3% in September while the Nasdaq gained 1.9%, and how did the third quarter end?

Key Highlights

• The SPDR Dow Jones Industrial Average ETF Trust (NYSEARCA:DIA) follows an index that fell 4.3% in September 2026 and 2.7% in the third quarter, closing at 50,906.05 on September 30.
• The S&P 500 dropped 0.5% in September by one published count and 0.4% by another, yet gained about 2% for the quarter, marking its tenth positive quarter in the past 12.
• The Nasdaq Composite rose 1.9% in September and about 2.5% in the third quarter to finish at 26,861.06, outperforming both the Dow and the S&P 500 over both periods.
• Higher oil prices and a surge in Treasury yields drove the September weakness, stoking fears of additional Federal Reserve rate hikes before the October 28 decision.

What September and the Quarter Looked Like

The SPDR Dow Jones Industrial Average ETF Trust (NYSEARCA:DIA) follows the index that suffered the biggest September damage. The Dow lost 4.3% for the month and 2.7% for the quarter. The S&P 500 slipped about 0.5%, its third losing month in the last four, but still advanced about 2% over the quarter. The Nasdaq Composite gained 1.9% in September and about 2.5% for the quarter. The third quarter also produced record highs across major Equity benchmarks, so the setback arrived after a strong run. Even so, three losing months in the last four show how fragile sentiment has been.

Why September Hurt

Oil was the first culprit. Brent Crude surged more than 14% during September, its third straight monthly gain, according to published market data. Treasury yields followed, with the 10-year yield climbing to levels last seen in 2007 earlier in the month. The Federal Reserve also raised rates by a quarter point on September 16, and traders have debated another move on October 28. Higher yields lower the present value of future earnings, which pressures stocks, and they also give investors a competitive alternative in bonds. The SPDR S&P 500 ETF Trust (NYSEARCA:SPY) tracks the index that absorbed these pressures better than the Dow.

Where October Starts

September is historically a weak month for stocks, and investors now face another test: October opens with jobless claims, the ISM Manufacturing index and a September jobs report. Traders priced about a 38% chance of an October hike after softer Inflation data. If hike odds rise again, yields could climb and weigh on equities. If data soften, the case for a pause strengthens and equities could stabilize. The Invesco QQQ Trust (NASDAQ:QQQ) tracks the Nasdaq-100, which has led the market, but seasonal patterns are tendencies, not guarantees, and the data calendar matters more.

Where Things Stand

The Dow lost 4.3% in September while the Nasdaq gained 1.9%, so the answer to the headline is that mega-cap technology cushioned the month while the older-economy benchmark absorbed the rate and oil shock. The SPDR Dow Jones Industrial Average ETF Trust (NYSEARCA:DIA) reflects an index down 2.7% for the quarter, even though the S&P 500 and Nasdaq finished the quarter higher. The balance of evidence is mixed. The next catalysts are Friday's jobs report and the October 28 Fed meeting.