My waist size changes a good bit in the course of a month, or for that matter, a week... within the last 10 years I would say that if I wanted to really fit, I'd get pants in 29/31, but I usually buy them in 30/30 because it's easier to find and more forgiving of a good Chinese meal. (I am not sure I can fit into 29" pants anymore, but the 30" ones are still comfy.)
About a year ago I bought a pair of pants which I really liked, size 12, from Lands' End. Do I remember the model? Nope. They were kind of loose, but that's okay -- they wouldn't get past my hips if they were to start to fall down, and I wouldn't need to unfasten them if I ate too much. And if I were really concerned, I could put on a belt.
Last month I went back to Lands' End and found some pants which I thought were similar, size 12. They were just way too loose. AND they didn't have belt loops! One was "wash in cold" and the other was "dry clean". I washed them both warm, and they were still way too loose.
Measured last year's models -- they had a 34 inch waist. This years? 36. And they DO fit past my hips. I'm either going to have to put some elastic in, or take some huge darts!
What I don't know is whether size 12 is the new size 16, or if they made them so I could show off my underwear. What I do know is that I'm annoyed.
(Yeah, I'm the same one who has found size 7 shoes that were too small and size 5.5 shoes (both women's) that were too large. Maybe it's just me.)