Anthropic is rapidly closing the gap on OpenAI in the enterprise AI market, with US business adoption of its Claude tools surging to 33% in March, up from 27% the prior month, according to payments data from Ramp. OpenAI maintains a lead at 35% but shows stagnant growth, with its ChatGPT business user base flat since November 2022 despite 900 million weekly active users. Anthropic's growth stems from its Claude Code platform and plug-ins tailored for automating white-collar tasks, attracting sectors like finance and professional services. Ramp's data, based on $100 billion in annual spending from 50,000 businesses, reveals Anthropic's user base tripled globally to 21 million in March, while ChatGPT downloads rose just 5%.