No longer seems to be the norm. If you check the back of any of the Big 4 patterns, looking to see how much yardage to purchase, they will all have an entry for 45″ width and maybe either 56″ or maybe 54″.
Alas, the days when 45 inches really was the width of a piece of fabric appear to be long gone. In the photo above, you can see how far the sleeve edges extend over then sides of the folded fabric. I know flannel shrinks, but when I first started using this pattern, that sleeve fit across the width. Not so any more.
Curious to see how wide this fabric really was, I fetched my trusty tape measure. 39 inches! 39 inches! Good thing I got that extra half yard, though I wonder when the pattern industry will awake, and update their yardage…because I don’t think we’re ever going to back to 45 inches being 45 inches.