The artificial-intelligence trade has reached the point where enthusiasm is no longer enough to support every technology valuation. Nasdaq 100 companies lost roughly $1 trillion in market value during the selloff, delivering Wall Street’s worst session since June and forcing investors to reassess how much technology exposure their portfolios can absorb.

This is not merely a bad day for a handful of technology shares. It is a test of the market’s dependence on mega-cap growth, index funds and the assumption that heavy AI spending will translate into durable returns. With the U.S. stock market still approximately 3.1% below its all-time high, the latest decline has sharpened the debate over year-end risk appetite.

AI spending meets valuation reality

For much of the recent market cycle, AI has functioned as both a business theme and a valuation defense. Companies associated with the technology could command investor attention because the expected opportunity appeared large enough to justify substantial spending. The latest selloff suggests that investors are becoming less willing to accept that argument without clearer evidence of how the spending will be converted into future financial results.

That change in attitude matters well beyond the companies building AI systems. It reaches platforms, advertisers and other businesses viewed as beneficiaries of the broader technology ecosystem, including Meta Platforms. The concern is not necessarily that AI has lost its strategic importance. Rather, the market is questioning whether the required investment and lofty expectations have already been reflected in valuations.

That distinction is critical. A powerful long-term technology may still produce a difficult near-term trading environment if investors begin demanding more discipline around capital spending and valuation. When expectations are elevated, even a change in sentiment can have an outsized effect on index performance.

Why index investors are feeling the pressure

The Nasdaq 100’s roughly $1 trillion loss in market value illustrates the concentration issue facing passive investors. An index fund can provide broad exposure to a benchmark, but broad exposure does not always mean evenly distributed exposure. When large technology companies represent a meaningful influence on the index, a technology selloff can flow directly through to retirement portfolios and other accounts tied to index performance.

That does not make index investing inherently flawed. It does mean investors managing technology concentration risk may need to distinguish between diversification by number of holdings and diversification by economic exposure. A portfolio can own many companies while remaining highly sensitive to the same forces: AI spending expectations, mega-cap valuations and changing appetite for growth stocks.

The pressure is especially relevant for retirement savers, who may have limited flexibility when a concentrated market leadership group turns lower. The latest session does not establish a long-term market direction by itself, but it does show how quickly a valuation debate can become a portfolio-level event.

Election uncertainty adds another layer

The selloff arrived ahead of Tuesday’s U.S. midterm elections, giving investors another source of uncertainty to weigh alongside AI spending and technology valuations. Markets may respond not only to the result but also to the prospect of policy uncertainty and shifting expectations around the economy.

That combination helps explain the caution surrounding year-end positioning. The market is already approximately 3.1% below its all-time high, while technology stocks are facing deeper pressure after Wall Street’s worst session since June. Investors may therefore become more selective, less willing to chase expensive growth narratives and more focused on how much concentration their portfolios carry.

The contrarian lesson is straightforward: the AI story may remain important, but importance is not the same as immunity from repricing. As NBC News reported on the technology selloff, the market’s concern is increasingly centered on the scale of AI spending and the valuations attached to it. Until that debate settles, the Nasdaq 100 remains a high-impact expression of both the promise and the vulnerability of the technology trade.