DSF

If a dozen t-shirts were a sample of the sizes and style I usually sell, it would look like this:

Women's T-shirt's: 5 (1 XS, 1 S, 2 M, 1 L)

Men's T-shirts: 7 (1 S, 3 M, 2 L, 2 XL)

We have an obesity problem in Mexico, but our average height is lower than the USA or Europe. So, even though we are usually shorter, larger sizes sell the most.

Does your average dozen look like this?

Depends. Difficult to give a breakdown by dozen as most of us generally work in 10's.
For workwear I tend to sell more L and XL than medium, and hardly any small or ladies. Probably Med 2, Large 4, XL 4, XXL 2
For event t-shirts for fun runs most of the size scale is down around the small/medium for the mens. The recent 200 shirt order I printed was S 60, M 70, L 60, XL 10