I have never measured so I don't know by how much the fabrics have shrunk. Often I can tell that they have (by the feel, by distortion at the selvedge edge, by the whole thing ending up cattywampus), but the only time I measured was when I had my Backing Saga last January, when the durned thing lost 11%.
I recently bought a set of 10" squares because I needed a lot of a particular color, but ony a little in any particular pattern. They were black so I soaked them in hot water with a squirt of dish detergent until they didn't lose any more color (several rinses!!), then dried them on a rack. I was cutting strip sets out of them, so I thought I'd just stack 'em up and let it rip...but nope, they had shrunk at several different rates. Only two out of 25 didn't shrink at all; most shrunk at least 1/2" in one dimension and several lost 3/4" in both dimensions. I had factored shrinkage into my cutting plan, so it didn't undo my project, but it did leave me shaking my head!
Alison