Why are Armholes so Deep on Patterns?

I get asked this question often, "why are armholes so deep on patterns?"

Hand knit designers are under a lot of pressure to produce a much larger size range for the patterns that they write. 

Sizes get larger not with the assumption that bigger sizes carry more body fat but with the assumption that the underlying bone structure is larger. Extra weight changes body shapes in a different way than the changes that occur due to larger or smaller underlying bone structures. Age also has an impact on body shape due to hormonal changes in women. It is for this reason that retail clothing changes depending on if the retailer is selling to teenagers, young women or mature women.

Alternative pattern systems in retail and sewing have separate categories to address these issues. As an example, plus, tall, and petite sizes in retail don’t just make things bigger or smaller, they adjust proportions as well.

Many knit designers are using the Craft Yarn Council measurements as a guidelines Check their website for further details. http://craftyarncouncil.com/womansize.html. The measurements are limited. For example there are no neckline standards.  Take note that the sizing charts do not include information about height. This is unique to the knitting world. 

Manufacturing and sewing patterns have height standards. In ready-to-wear these variations are dealt with by a number of different size ranges that target a more narrow scope of body types. Most people figure out what size range fits by trial and error when shopping for clothing. Yet knitters are asking patterns to somehow cover all of these size ranges in a single pattern.  Hand knit designers are trying to respond to requests for more size options by grading patterns up in unusual ways, that don't really work for everyone. The goal is to provide as many options as possible. 

The alternate sizing systems in both retail and sewing use height target ranges. There is an underlying assumption in some systems that smaller sizes are for shorter women and larger sizes will fit taller women. However, the variations are relatively small, usually less than four inches for total height. In knitting patterns, it has become standard for lengths to increase at much greater increments than in ready-to-wear, as sizes increase. One pattern source that sizes from 36 to 54 has eight inches difference from the shoulder to the high hip. To put this into perspective, if the 36 was five feet tall, the 54 would be approximately 6 feet, 4 inches. This is a way of eliminating the need for petite, average and tall size categories that creates a whole new set of problems. 

To address the topic of this post, the knitter can wear a garment with a too deep armhole but not one that is too short. Designers are trying to avoid that problem for the knitter. What this means is that the individual knitter must always check the required measurements against those in the pattern and adjust to more closely match those of the intended wearer.