19%About 1 in 5longer: experienced open-source developers took 19% more time on tasks when allowed AI tools (early-2025 test; METR now calls it out of date)
19% longer: experienced open-source developers took 19% more time on tasks when allowed AI tools (early-2025 test; METR now calls it out of date) (Feb to Jun 2025, METR (Model Evaluation and Threat Research), METR research notes)
StudyChecked at source, 23 Oct 2026All sizesGlobalWeb and software development · AI productivity
19% longer: experienced open-source developers took 19% more time on tasks when allowed AI tools (early-2025 test; METR now calls it out of date) (Feb to Jun 2025).
19%
the latest figure (Feb to Jun 2025)
Study
type of source
Why you can trust it. METR (Model Evaluation and Threat Research), METR research notes: study, experiment or academic paper. 16 experienced developers from large open-source repositories, 246 real issues randomly assigned to AI allowed or not.
METR (Model Evaluation and Threat Research), METR research notes
Source type
Study: Experiment or academic paper
What it measures
19% longer: experienced open-source developers took 19% more time on tasks when allowed AI tools (early-2025 test; METR now calls it out of date)
Data period
Feb to Jun 2025 (ends 30 Jun 2025)
Published by the source
10 Jul 2025
Who is counted
16 experienced developers from large open-source repositories, 246 real issues randomly assigned to AI allowed or not.
In the source's words
Surprisingly, we find that when developers use AI tools, they take 19% longer than without—AI makes them slower.
Checked at source
23 Oct 2026: Read on metr.org. 16 developers, 246 issues. METR's page now says these results are out of date; Feb 2026 update estimates -18% (CI -38% to +9%) for returning developers and -4% for new ones, with strong selection effects.
Reuse
Cite with attribution. Randomized controlled trials on AI and developer productivity; METR itself marks the July 2025 result as out of date.
Next expected update
Irregular (METR (Model Evaluation and Threat Research), irregular)
24 Feb 2026Method change-18% METR update: for returning developers METR now estimates -18% (CI -38% to +9%), which it reads as some evidence of speed-up, but it says the new data is unreliable because many developers refused to work without AI.
Cite this number
APA
METR (Model Evaluation and Threat Research). (2025). 19% longer: experienced open-source developers took 19% more time on tasks when allowed AI tools (early-2025 test; METR now calls it out of date). Via digitaltreed, https://digitaltreed.com/statistics/web-development/experienced-developers-slower-with-ai-2025
MLA
"19% longer: experienced open-source developers took 19% more time on tasks when allowed AI tools (early-2025 test; METR now calls it out of date)." METR (Model Evaluation and Threat Research), METR research notes, Feb to Jun 2025. digitaltreed, https://digitaltreed.com/statistics/web-development/experienced-developers-slower-with-ai-2025.
HTML link
<a href="https://digitaltreed.com/statistics/web-development/experienced-developers-slower-with-ai-2025">19% longer: experienced open-source developers took 19% more time on tasks when allowed AI tools (early-2025 test; METR now calls it out of date)</a> (METR (Model Evaluation and Threat Research), Feb to Jun 2025)
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FAQ
Questions about this number
What is the latest figure for AI productivity (Global)?
19% longer: experienced open-source developers took 19% more time on tasks when allowed AI tools (early-2025 test; METR now calls it out of date), for Feb to Jun 2025, according to METR (Model Evaluation and Threat Research), METR research notes. We checked it at the source on 23 Oct 2026.
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