With the rise of the barefoot running movement, a question that a lot of people are asking is “What is shoe stack height, and why is it important?”
Although some people use the term “stack height” to refer to the difference between heel stack height and forefoot stack height, it's best to refer to this difference as “forefoot drop” or “heel drop”. Forefoot drop gives you an indication of how “wedgy” the shoes are; shoes that leave your heel higher than your forefoot will have a higher number for forefoot drop.
The minimalist shoe movement is trending toward lower stack heights and smaller forefoot drops. The importance of smaller stack heights is that shoes with less midsole material and outsole provide for more road feel and a more “barefoot” running experience. In fact, New Balance's upcoming Minimus Zero (scheduled for release in early 2012) distinguishes itself by having zero forefoot drop – the same stack heights in both the heel and forefoot.