I got an interesting question today about raw denim and how they shrink. Here's their question, "Just want to ask if the waist of the raw jeans shrink too after washing? and will the whole jeans shrink?"
As far as I understand, the idea is to wear the raw denim jeans for as long as you can, before you wash them. Usually six months to a year. The reason for this is that the wear stretches them in all the right places. On your knees, the crotch area, the waist and wherever else. When you wash them then later, they shrink back to the normal size, but the fit is better now, because they've been worn in. They're also much softer now.
I could see the person's concern though, because their new raw denim might still feel too tight, and they're scared that after a wash they'll end up with jeans that are too small around the waste. This should not be the case if you've worn them for a while, because everything stretches from the wear, as does everything shrink with the wash.
I only started wearing a belt with my jeans every day after the third month, when the waste was so stretched, that the jeans had trouble staying up. After the wash, I think the fit should be really good.