HOW TO FIT INTO SMALLER VINTAGE SIZES
If you're vintage shopping and find a piece that's labeled a size or two smaller than yours but has elastic shirring/smocking in the top/sides or elastic in the waistband go for it! Chances are, it will have enough stretch to accommodate going one, two or even three sizes up.
The trick is to find pieces that have loose/free bottoms such as flare skirts, palazzo pants and circle dresses.
80's dresses, skirts, and palazzo pants fall perfectly in this category and I often use this trick when vintage-shopping online. I also apply this rule when in a brick & mortar shop and wont overlook a piece labeled a smaller size. I'll take it to the dressing room and give it a try. I also find the pieces requiring a little bit of stretch tend to have a more tailored & flattering fit for my figure which is smaller on top and curvier on the bottom.
Elastic shirring/smocking in the back of my vintage dresses & in the waist of a few of my vintage skirts and shorts