The Nasdaq Has Fallen in 48% of Septembers Since 1971. Here's What That Means for Nvidia and Micron.

Historical market data reveals that September is often the most challenging month for technology equities, driven by a calendar phenomenon known as the September Effect. Since its inception in 1971, the Nasdaq has averaged a return of -1% in September, standing as the only calendar month with a negative long-term average. While the index still finishes positive approximately 52% of the time, the magnitude of declines when it falls tends to be significantly steeper and more concentrated. Institutional factors contribute heavily to this seasonal weakness. Portfolio managers returning from summer breaks frequently re-evaluate portfolios, trim high-performing winners, and execute tax-loss harvesting ahead of fiscal year-ends in September and October. Mega-cap artificial intelligence leaders like Nvidia and Micron Technology face heightened volatility as high liquidity makes them prime candidates for profit-taking and portfolio rebalancing. Market implications will center on earnings digestion and seasonal positioning. With Nvidia reporting in late August and Micron scheduled for September 30, analysts suggest maintaining disciplined position sizing while looking past short-term seasonal volatility to broader multi-year AI infrastructure fundamentals.