After reading Jen's blog, I was curious to find out more about EPS. The following is a pretty good write-up:
"The percentage system is based on two general sweater shapes: the yoke and the drop shoulder. In the yoke style, the body is knit in the round to the underarms, as are the sleeves, and all three are joined to work the shoulders and neck in the round. Any number of different finishes can be executed once the body and sleeves are united including raglan, yoke, saddle shoulder and others. The drop shoulder style is worked in the round all the way to the neck with steeks used for the armholes or divided at the armholes and worked back and forth to the neck. The sleeves are joined afterward.
All calculations are based on the number represented by the variable K. K is your "key number" and stands for the number of stitches around the largest part of the body of the garment. You can figure out this value by multiplying your number of stitches per inch (gauge) by the circumference of the garment in inches. For example, a garment knit at 5 stitches per inch that is 50 inches around would result in K = 250. All further variables are gleaned from this initial number.
You can use it to calculate the dimensions of your favorite sweater in order to recreate the fit in a new sweater. You can also adjust the formulas to reflect the current fashion trends in terms of sleeves and fit. Create a snugger silhouette by reducing the percentage of stitches in the wrist and upper arm of the sleeve, create a boat neck by increasing the number of stitches at the neck, increase with greater or lesser frequency to change the overall shape of the sleeve."
Thank you, Elizabeth Zimmermann!