ChatGPT Takes the Wheel: AI Manages a Stock Portfolio and Outperforms the Market in Just 4 Weeks

In a fascinating blend of technology and finance, a Reddit user has sparked widespread discussion by letting ChatGPT manage a live stock portfolio. The experiment, shared on r/dataisbeautiful, shows the AI outperforming key benchmarks over four weeks, leading to viral attention on X (formerly Twitter). Entrepreneur Greg Isenberg amplified the buzz with a thread analyzing its broader implications for markets and investors. Here’s a deep dive into the setup, results, and what it could mean for the future of AI-driven investing.

The Experiment: Letting AI Call the Shots

The project, spearheaded by Nathan Smith (Reddit user OpenArcher7341), is a six-month test running from June 27, 2025, to December 27, 2025, to assess how well a large language model like ChatGPT can pick and manage micro-cap stocks — companies with market caps under $300 million — with a modest $100 budget. Unlike simulated trades, this uses real money, though it’s emphasized as an educational exercise, not financial advice.

The methodology is straightforward yet rigorous:
- AI Role: ChatGPT (using the GPT-4o model) acts as a “professional-grade portfolio strategist,” with full control over stock selection, position sizing, risk management (e.g., stop-losses), and order types. It’s restricted to U.S.-listed micro-cap stocks, including over-the-counter (OTC) ones if tradable.
- Prompting: The AI receives a…