http://www.reifenbreiten-datenbank.d...e-Big%20Apple-
20x2.00.html
Reifenbreiten-Datenbank

..this page has thousands of entries from people who measured their tire width, with rim width and pressure. It's german, but tire model names and parameters are universal. The database has a clear tendency on Schwalbe tires.
Around ten years ago it boiled up here in germany why Schwalbe tires are always narrower than specced. Schwalbe stated that they give the width that they measure in the lab on a "reference" rim, that equals 2/3 of the specced tire width, for example 40mm inner width for a 60mm tire. And they measure with max. pressure. Will look for the article and link. Most other manufacturers give more realistic digits. The web is full of that topic, always about the same manufacturer.