Thanks flippalicious. I just did the test. I took a small hairband and wrapped it very tight 2x around. I got 4 inches and a quarter. Then I thought "This could be snugger", so I wrapped it 3x around. This time my ponytail came out 4 inches exactly, although I still wasn't able to catch some of the shortest layers in there. So I'm guessing I'm closer to high density, even with the thicker strands. For instance, my mother has medium-fine hair that she often wears in a ponytail and it's definitely fatter than mine. I'm betting her tail is 5 inches all around.
3A - C, HP, ME, HD. (Coarse, High Porosity, Medium Elasticity, High Density.)

CG since Nov. 2012

Poos: SM Moisture Retention + Yucca Baobab, TJ's Tea Tree Tingle
Condish: TJ 'sTea Tree Tingle*, SM Moisture Retention* + Curl & Shine + Yucca Baobab, Yes to Blueberries
Stylers: KCKT*, SM Curl Enhancing Smoothie* + Curl & Style Milk*, KCCC*, FSG*, CJ Pattern Pusha, Curl Keeper
Sealers: Jojoba* or Grapeseed* oil

* = HG