A question about "chest" measurement

[Gauss17]

A question:

Normally when a suit, shirt, or what-have-you is bought, there is a chest measurement listed. Sometimes in pit-to-pit, sometimes in total circumference. However, I am noticing, at least in myself, that my "back" measurement appears larger than my "front" (chest). You might say you take this into account with a total circumference measurement, but it seems to me that this neglects the upper portion of the shoulders (shoulder blade area). When I got to my tailor, I personally find the chest measurement (front) appears good or slightly on the large side, but the "across-the-back" needs to be let out (my tailor confirms this and always suggests it when I take a jacket to be altered). The shoulders are typically fine. My shirts are similar. I have a fair amount of excess fabric in front, but the back is tighter. I asked if it was my posture and she (my tailor) said no. Is this typical, am I built oddly, or am I just in need of some enlightenment as far as articles of clothing are measured and cut?

 

[Despos]

Measurements don't reveal symmetry and depth. You may have a small chest and broad back or the opposite, broad chest and flat back or you may have front/back depth and narrow back and chest. Shapes vary like this, 0 or this, O, etc..