This video illustrates how bizarre women's clothing sizes are

The world of sizes for women's clothes is bizarre. A woman could wear a size 2 in one brand's apparel, and a 6 in another.

In June, a woman posted a viral letter to H&M for not being able to fit into their size 16 jeans...while wearing a size medium shirt. 

In a recent video for Vox, a reporter tried on three different pairs of pants in the same size and three different stores - Zara, Topshop, and Forever 21 - to prove that this theory was true. Then, Vox set to find out why.

The video reveals the history of women's apparel sizing, from the first ever data set that determined sizing - which was comprised out of data from poor, likely underfed Caucasian women and nixed in 1983 -  to today's vanity sizing.

Sizing today is used as a marketing tool, the video notes. This can vary from store to store (which makes sense, given how different stores target different demographics).

"I think we're more aiming for our own target markets," Lynn Boorady, associate professor and chair of fashion and textile technology department at SUNY Buffalo State said to Vox. "So, when Abercrombie & Fitch does their sizing, they're sizing to their targeting market, not to me. We kept tweaking that information nn until we sold more garments and could lower the return rate."

But for people who are fretting about not being able to slip into a smaller size, Boorady sums up: "They are just random numbers, they don't mean anything."

The video is below.