The gauge broke: devs felt 20% faster with AI, measured 19% slower

A controlled trial of experienced developers found they felt approximately 20% faster using AI coding tools while objectively performing 19% slower, revealing a dangerous misalignment between perceived and actual productivity. The study attributes this to AI accelerating typing—not the actual bottleneck for expert developers—while adding significant overhead in prompting, waiting, and reviewing often-flawed output. Broader data across thousands of developers shows increased code generation and merging with no improvement in delivery, suggesting the real bottleneck has shifted to review and verification stages that weren't adequately staffed for the volume AI produces.