LME already has some liquid in it. Making the yield slightly less than DME per volume but much more exaggerated when measured by weight.

While maltsters do thier best for consistency yields will vary between batches and maltsters.

So you really can't have any accurate static value of yield for LME / DME or even All Grain. 

Maltsters have data sheets for all of thier products. Recipes should be adjusted accordingly. A well recorded original recipe will include malt yields, AA % etc. Recipies are then adjusted at brewing for duplication and consitancy of a beer. Most issues are corrected by correcting OG.

**Answer: The static ratio is an average and guess at best.**

**Palmer uses 1.25/1 ratio which is a ratio used by most. IE 6 lb DME = 7.5-7.6lb LME**