How Real Are AI Coding Productivity Gains? A Review of NBER w35275
A review verifying three generations of AI coding tools against data from 100k+ developers โ and why a +180% commit gain decays to +30% in shipped releases.
- Marginal and cumulative effects reconcile exactly across all six production layers
- Only Claude Code (+29.2%) translated into releases โ the pipeline, not the tool, is the bottleneck
- Full reliability assessment: conflicts of interest, contradicting RCT evidence, coverage limits
