I do want to add, that part of the reason that sizes vary so much is partially do to the styling/genre of the clothing. There is actually a difference in design between juniors clothing, and misses, just as there is between womens (or plus) and misses. This is why an 18 in misses fits differently than a 18W or 18 plus.
The same thing happens with infants/toddler clothing. 24 months and 2T fit a child of the same weight/height, but there are differences in the styling, based on whether it is a child, or a larger infant wearing that particular size.
Juniors normally fall in odd sizes, and misses in even-so that you can tell them apart. Some clothing are made to fit both, and might say size 7/8 or 13/14, etc. on the tag.
Juniors clothing are meant more for teens-the hips are narrower, the room for the bust isn't as large, etc. basically meant for a teenage figure. A misses (even sizing) is meant for a mature female-with rounder hips and fuller bust.
If a woman is straighter hipped and a B cup, she is going to fit into juniors better than a C cup female with a more hourglass shape-even if they are the same weight. So, depending on how developed the figure is, is why misses or juniors might fit one individual better than the other.
The plus sizing overlap (usually starting at 14W) is the same way. A plus size will allow a little more room in the bust, shoulders, upper arms, calves, etc. than a regular size 14 will.
(I do seamstressing, BTW...that's how I know.
)
