I am a hand dyer and art quilter. I am not familiar with the fabric production process, but I can tell you the the majority of shrinking of cotton occurs in the washer. For some others (flannel or wool) they may shrink more in the dryer. When I decide to make a quilt and dye my cottons, I pre-wash in hot to remove the sizing that is on the fabric. I personally never use any fabric without pre-washing. I have been burned. I air dry the fabric that I dye and press it with an iron when still wet. I believe (maybe I am wrong) that the general amt of shrinkage of cotton fabric depends on the quality of the cotton you buy. If I see a cheap white cotton and I am tempted to buy it, it does tend to shrink more than the better quality cotton. Also, if you dry your fabric in the dryer...DON'T use a fabric sheet in the dryer. It tends to dull your rotary blades more quickly.