Saturday marks two years since OpenAI posted an oddly named widget called ChatGPT to the web. It became the fastest-growing app in history, with about 200 million active users today. The six biggest have seen their market capitalizations grow in aggregate by more than US$8 trillion since its launch. The tech sector has driven a 30% gain in the S&P 500 since January 2022, while small-cap companies have seen a more modest 15% return.