In all grain brewing, it's nice to get an accurate calculation of extract efficiency, so we know exactly what our pre-boil gravity will be and have an idea of how the resulting beer will turn out in terms of final gravity. Most of this has to do with calculating the efficiency of your particular brewing system (and increasing that efficiency, if desired).
A smaller part of this number involves how much extract potential there is for a particular malt, which isn't always clear on a malt analysis. I came across this formula for more accurately calculating the extract yield potential based on the course grind extract yield and the moisture content. Moisture content decreases extract efficiency, and most malt analyses I've seen don't factor this in to extract yield (though some do).
So if you can find these two numbers, "Extract, dry basis course grind (DBCG)" and "moisture content," you can factor this in to your efficiency calculation. I just happen to be particularly particular about my potential extract calculations, so read on if you share my obsession with trying to get the most accurate calculations possible.
This is from Gregory Noonan's New Brewing Lager Beer, p 13.
DBCG / (1 + moisture content) - 0.002 = as is course grind extract yield
(percents are expressed in decimals)
For example, if a malt analysis reads 78% dry basis course grind extract yield potential, and the moisture content is 3.5%
0.78 / (1 + 0.035) - 0.002 = 0.752 or 75.2% as-is extract yield
So you can see, this makes a small, but significant difference, especially for base malts of which you are using several pounds in your mash.
Hope this is helpful to anyone who was wondering.