Why do so many women wear the wrong bra size?

Bra size isn't just letters. AA, A, B, C... are the cup size (aka breast size), there is also the number for your "band size", the underbust measurement.

How can I tell if my bra fits correctly?

Things need to check :

• BAND: when hooked around your body, you should be able to snake the width of your finger underneath.  In other words, it should be tight, but not so tight it creates bulge around the band of the bra

• CUP: looking in the mirror, your boob should fit in the cup without squeezing out the top (which will create a "double boob" in a t-shirt) or leaving extra material (which will also look funny in a t-shirt)

• STRAPS: shoulder straps should again be tight without digging into your skin, and not loose enough to fall down your shoulders.

What lingerie brand is sexier than Victoria's Secret?

I don't find Victoria's Secret particularly sexy or well designed at all. The designs are very generic and fussy. For sexiness it panders to the obvious (red satin with black lace anyone). I'm sure I'm in the minority, though.

I do like Girly Things, which are lovely as mentioned previously.

Still let me introduce to what I think are much classier and sexier brands. I think the British and the French do the most luxurious and sexiest lingerie of all so that's how I've categorised them. There are definite similarities of style within these categories.

Who invented the bra?

The first bra was patented in 1914 by Mary Phelps-Jacobs an American.

Mary Phelps-Jacobs patented her bra design under the patent name of Caresse Crosby.
Phelps Jacobs couldn't get much interest for her idea and sales were minimal, so for $1500 she sold the rights to Warners...and a few years later just change that fifteen hundred patent valuation for fifteen million dollars... Warners have been involved in bra production ever since. Within a year, breasts were measured in inches rather than being categorized small, medium or large.

Why do all women wear a bra, regardless of cup size?

Firstly, some women don't. As mentioned by others, a small cup size and nipples that are not noticeable, or a more brazen outlook regarding their visibility, makes this entirely practical.

Most women find them more comfortable than not wearing one.

How does a lingerie store determine what quantity of each bra size to carry?

 Generally speaking, the optimal amount of stock that is kept on hand at any given time is based upon historical sales.  Of course, the heaviest inventory levels would go to the most popular-selling sizes, progressively decreasing in size in unison with sales.