Goldman Sachs Ex-AI S&P 500 Index Shows 6.7% Gain vs 18.3% With AI

Goldman Sachs has built a version of the S&P 500 that removes AI-related stocks, and the performance gap between the two indices is striking. Over the past six months, the standard S&P 500 gained 18.3%, while Goldman's ex-AI variant returned just 6.7%. The 11.6 percentage point difference reveals how heavily the broader market's gains depend on a narrow group of artificial intelligence names, and it raises uncomfortable questions about concentration in the world's most followed equity benchmark.

What is the Goldman ex-AI index?

Goldman Sachs constructed a custom index that mirrors the S&P 500 but strips out companies classified as AI-related. The goal is to isolate how much of the benchmark's return comes from the artificial intelligence trade. By removing these firms, the bank created a portfolio that reflects the US equity market without its most powerful recent driver.

The ex-AI index gained 6.7% over the same six-month window. That is a solid return by historical standards, but it pales next to the 18.3% posted by the full S&P 500. The gap suggests that AI-related companies have been the primary engine of equity gains in this period, and that the rest of the market has participated only modestly in the rally.

Why does the 11.6 percentage point gap matter?

The spread between the two indices is a measure of concentration risk. When a single theme drives most of the market's return, portfolios that appear diversified may be far less balanced than they seem. Investors who believe they hold broad exposure to the US equity market may, in practice, hold a concentrated bet on AI.

This is not a new phenomenon. The S&P 500 has long been weighted toward its largest constituents, and technology companies have dominated those top slots for several years. What the Goldman index makes visible is the degree to which one narrative, artificial intelligence, has come to define the market's direction. The index strips away the story and shows the underlying numbers.

The AI trade has defined the 2026 market

Artificial intelligence has been the dominant investment theme across global equity markets. Companies involved in AI infrastructure, software, and services have attracted enormous capital inflows. Their share prices have risen sharply, and their weight in major indices has grown accordingly. The result is a market where a handful of firms can move the entire benchmark.

The S&P 500's heavy allocation to mega-cap technology names means that when AI stocks rally, the index rallies. When they stall, the index struggles to find upside momentum elsewhere. Goldman's ex-AI index strips out that effect, showing what the market looks like without the AI tailwind. The answer, according to the data, is a market that still rises but at a far slower pace.

The 6.7% return of the ex-AI index is still positive, which tells us that non-AI sectors have made gains. But those gains are modest compared to the AI-driven portion of the market. The divergence underscores how uneven the recovery has been beneath the surface, and it challenges the assumption that a rising tide is lifting all boats.

What this means for portfolio construction

The Goldman index highlights a risk that many investors may overlook. A portfolio tracking the S&P 500 is not a neutral bet on the US economy. It is, in significant part, a bet on a handful of technology companies and the AI narrative surrounding them. The index fund in a retirement account may be more concentrated than the account holder realizes.

Financial advisors and institutional investors use tools like this to measure factor exposure and concentration. The ex-AI index serves as a diagnostic, revealing how much of a portfolio's performance is tied to a single theme. For retail investors, the lesson is that index funds may carry more concentrated risk than their broad branding suggests, and that understanding what drives returns is essential to managing risk.

Diversification within the S&P 500 is limited by its market-cap weighting scheme. The largest companies exert outsized influence on returns. When those companies share a common theme, as they do with AI, the index's exposure to that theme becomes even more pronounced. True diversification may require looking beyond the headline index.

What to watch next

Several factors could narrow or widen the gap between the AI and ex-AI indices. A rotation out of AI names into other sectors would compress the difference. Continued AI outperformance would widen it further. The direction of that rotation will depend on earnings, macro data, and investor sentiment.

Earnings reports from major technology companies will be critical. If AI-related revenue growth slows, the premium embedded in those valuations could unwind quickly. Conversely, sustained AI spending by corporations would likely keep the gap wide. The next round of quarterly results will test whether the AI trade still has momentum.

Macroeconomic conditions also matter. Interest rates, inflation data, and Federal Reserve policy all influence whether investors favor high-growth AI names or rotate toward value and cyclical sectors. The six-month window captured by Goldman's index is a snapshot, and the relationship between AI and the broader market can shift as the economic backdrop changes.

Regulatory developments around artificial intelligence could introduce new risks. Governments worldwide are considering rules for AI development and deployment. Any significant regulatory action could affect the valuations of AI-heavy companies and, by extension, the S&P 500 itself. Policymakers in the United States, Europe, and Asia are all active in this space, and their decisions could reshape the AI investment landscape.

FAQ

**How did Goldman Sachs define AI-related stocks?** Goldman Sachs classified companies based on their exposure to artificial intelligence as a business driver. The exact methodology is proprietary, but the index removes firms whose fortunes are closely tied to AI demand and development. The classification likely includes companies across semiconductors, cloud computing, and software.

**Is the ex-AI index available for investors to buy?** The index is a research tool created by Goldman Sachs. It is not a tradable product itself, but it informs how the bank advises clients on portfolio construction and risk management. Investors seeking similar exposure would need to build their own portfolios or find funds with similar mandates.

**What does the gap say about market concentration?** The 11.6 percentage point spread indicates that a narrow group of AI-related companies has driven the majority of the S&P 500's gains. This level of concentration increases the risk that a reversal in AI sentiment could drag the entire index lower. It also suggests that the broader market's health is more fragile than the headline index implies.

**Will the gap persist?** That depends on whether AI companies continue to outperform the broader market. If the AI trade remains strong, the gap will persist or widen. If capital rotates into other sectors, the two indices could converge. Much will depend on earnings growth, macro conditions, and whether the AI narrative continues to attract capital.