Ten lossmaking artificial intelligence start-ups have gained close to $1tn in valuation over the past 12 months, an unprecedented increase that adds to fears about an inflating bubble in private markets that could spill over into the wider economy.

OpenAI, Anthropic and Elon Musk’s xAI have seen their values marked up repeatedly over the past year amid a rush to back young AI companies. Smaller groups building AI applications have also surged, while established start-ups including Databricks have soared after embracing the technology. 

US venture capitalists have splashed $161bn over the year to date on a technology whose promise has not yet been matched by major economic gains. That equates to two-thirds of their total spend, according to PitchBook.