Developers Think AI Makes Them 24% Faster. It Actually Makes Them 19% Slower.

Developers using AI coding tools believe they're 24% faster. Measured objectively, they're actually 19% slower. That's a 43-point perception gap, and it explains a lot about why AI tool adoption keeps rising while trust keeps falling. The data comes from the METR study, which measured experienced open-source developers working on their own repositories with tasks they selected themselves. This wasn't a lab experiment with toy problems. These were real developers doing real work, and the AI made them measurably less productive while making them feel productive.