One of the biggest debates among stock market investors in 2026 has been: "Is there an AI bubble?" Some investors are worried that tech stock valuations are too high, that the S&P 500 index is too top-heavy with artificial intelligence (AI) stocks, and that AI hyperscalers are spending too much on AI data centers. But here's one thing I wish all investors knew about the stock market: Instead of an AI bubble, we might be seeing the beginnings of a widespread AI boom. And they're reporting profit margin gains of 1.5% to 1.8% directly linked to AI tools and automation. Buying an S&P 500 ETF could be a smart move for long-term investors.