I bet you are wondering why I'm covering the topic of dress sizes in a math column? In fact, I suspect you believe there is no reason it should be covered here since you take whatever size you take.
Prior to the 1940's dress sizes were not standardized as they are today. For children, their sizes were based upon their age so a 12 year old was expected to take a size 12 while women purchased patterns based on their bust size.
In the 1940's sizes became more standardized when the WPA measured 100,000 women to create the first real standardized charts since ready to wear still did not fit as well as home made. Even as late at the 1930's the size of the dress was determined by the bust measurement except the size listed was half the bust measurement. In other words, a size 18 was made for a 36 inch bust.
By 1958 the Bureau of standards published an official guide to pattern sizing. At this point a size 8 was made for someone with a 31 inch bust, 23.5 inch waist, and a 32.5 inch hips. By 2008, a size 8 increased five to six inches for each of the three measurements. That is quite a large increase over 30 years. In addition, Marilyn Monroe was a perfect size 12 which is now a size 6.
So lets look at the changes in size from 1958 to the present. I've put the numbers on a spread sheet. The top are measurements for the bust while the bottom are measurements for the hips. Both are in inches.
So now what to do with this information?
1. Create line graphs out of the numbers.
2. Determine percent increases to see if the increases were constant. They might need to determine a yearly increase to make this work.
3. Have students note that a size 12 in 1958 was not the same as a size 8 in 1970 and ask them why?
4. Have students look at the size 0 and determine if it matches any earlier sizes.
5. Ask students why the measurements assigned to each size got larger over time. (Its a sales tactic. If a women can buy a garment with a smaller size, she feels better about herself and she is more likely to buy it.)
This is a real world look at sizes and marketing. Let me know what you think. Have a good day.