The SPDR S&P 500 ETF Trust (SPY  ) has appreciated by over 30% in the past eight months, a dichotomy from the once-bearish market. The 10 largest artificial intelligence (AI) stocks now comprise an outsized part of the S&P 500, indicating investor optimism in AI's future.

The Data: A post on X shared a Bank of America chart depicting the "Big 10" AI stocks as a percentage of the S&P 500's total value.

The top 10 AI-related stocks now hold a record-high share of the S&P 500, more than doubling their weighting since early 2023, before the release of OpenAI's ChatGPT.

The "AI Big 10": The following companies comprise the so-called AI "Big 10."

• Microsoft Corp (MSFT  ), 6.82% of the S&P 500.
• NVIDIA Corp (NVDA  ), 6.73% of the S&P 500.
• Alphabet Inc (GOOGL  ) (GOOG  ), 4.49% of the S&P 500.
• Amazon.com Inc (AMZN  ), 3.92% of the S&P 500.
• Meta Platforms Inc (META  ), 2.62% of the S&P 500.
• Broadcom Inc (AVGO  ), 1.73% of the S&P 500.
• Qualcomm Inc (QCOM  ), 0.52% of the S&P 500.
• Advanced Micro Devices, Inc (AMD  ), 0.52% of the S&P 500.
• Applied Materials, Inc (AMAT  ), 0.42% of the S&P 500.
• Micron Technology Inc (MU  ), 0.35% of the S&P 500.

Why it Matters: The S&P 500's sky-high performance amid tough macro conditions can largely be attributed to the proliferation of AI. On its own, NVIDIA's eye-popping performance has accounted for around half of the S&P 500's advance in 2024. In the meantime, other industries have struggled.

In recent months, other AI and AI-adjacent stocks have been added to the index. Super Micro Computer Inc (SMCI  ) was added to the S&P in March, while cybersecurity company CrowdStrike Holdings Inc (CRWD  ) will be added next week.