Centers for Disease Control and Prevention data show that the average American woman today weighs about as much as the average 1960s man. And while the weight story is pretty straightforward — Americans got heavier — the story behind the dress sizes is a little more complicated, as any woman who's ever shopped for clothes could probably tell you.
As Julia Felsenthal detailed over at Slate, today's women's clothing sizes have their roots in a depression-era government project to define the "Average American Woman" by sending a pair of statisticians to survey and measure nearly 15,000 women. They "hoped to determine whether any proportional relationships existed among measurements that could be broadly applied to create a simple, standardized system of sizing," Felsenthal writes.
Sadly, they failed. Not surprisingly, women's bodies defied standardization. The project did yield one lasting contribution to women's clothing: The statisticians were the first to propose the notion of arbitrary numerical sizes that weren't based on any specific measurement — similar to shoe sizes.
The government didn't return to the project until the late 1950s, when the National Bureau of Standards published "Body Measurements for the Sizing of Women's Patterns and Apparel" in 1958. The standard was based on the 15,000 women interviewed previously, with the addition of a group of women who had been in the Army during World War II. The document's purpose? "To provide the consumer with a means of identifying her body type and size from the wide range of body types covered, and enable her to be fitted properly by the same size regardless of price, type of apparel, or manufacturer of the garment."
The standard included the first modern women's clothing size charts, and it provides the first data points in the charts above. Women's sizes ranged from 8 to 42. A size 8 woman had a bust of 31 inches, a 23.5 inch waist, and a weight of 98 pounds.
The government updated these standards again in 1970. But already, manufacturers were getting restless, Slate's Felsenthal writes. It became apparent that the "representative" women measured for the standard weren't representative at all. Non-white women were excluded. The group of women from the Army were almost certainly fitter than the average American woman. By 1983, the government ditched the standard completely. Manufacturers were left to define sizes as they saw fit.
Enter the era of vanity sizing. Clothing manufacturers realized that they could flatter consumers by revising sizes downward. The measurements that added up to a size 12 in 1958 would get redefined to a size 6 by 2011. And different manufacturers defined sizes differently, too — this fascinating New York Times graphic from 2011 shows how a size 8 waist measurement could differ by as much as five inches of cloth between different designers.
The American Society of Testing and Materials, a nongovernmental international standards organization, began trying to restandardize women's sizes in the 1990s. But by then, the sizing genie was well out of the bottle. But if you've dealt with the frustration of buying or trying on women's clothes recently — particularly if you're short, tall, or in any way idiosyncratically shaped — you know that most manufacturers ignore these standards. It doesn't help that ASTM charges for access to its sizing tables. What good's a standard if you keep it under lock and key?
So women are left to navigate the chaos of arbitrary sizing on their own. So much for enabling women "to be fitted properly by the same size regardless of price, type of apparel, or manufacturer of the garment," as the government's 1958 standard loftily envisioned.