the two year old pile has shrunken by 3/4th's. The molded leaves at the very bottom are almost ready to use...but not quite.
Wow, that's been setting there for two years! That's decomposing slow! How big is the pile? Did you add anything else? What kind of leaves?
The pile in your hand, that was the almost decomposed leaves at the very bottom? If so, then yes, that's slow. You should have a little layer at the very bottom by now.. Dig deep, mix in some vegetable scraps, grass clippings, any green plant matter. This will speed up decomposition, you could have that pile compost in a couple months. I should ask what are you using it for? Some like leaf mold..
Leaves, and other types of organic matter, that simply sit around for long times often loose valuable nutrients through leaching and/or gassing off. leaves are a valuable resource if used shortly after the fall off the trees, and can be a decent resource if piled up and let decay into leaf mold. The C:N ratio of freshly fallen leaves is around 40:1 while leaves left to the whiles of nature soon reach an 80:1 C:N ratio.
You hear Kimmsr, leaves are roughly 60-80:1 carbon to nitrogen. For hot compost, you want a pile with around 25-30: 1 carbon:nitrogen. So you can see why I tell you to add nitrogen, green material because it will make compost about half the time.
Leaves in the forest fall to the ground, layer and compact naturally, exclude oxygen and then they mold. To some extent they are digested by worms, but mostly they just form leaf mold...from the bottom up. If I mix it up and aerate it I stop that process. Three year old leaf mold is worth 100 times as much as newly fallen ones and there is no gassing off of nitrogen. Leaf mold, though it is not high is nutrients is a superior potting mix. My four piles average about 600 cubic feet each when I first put them up. A finished pile will be about 100 cu.ft.
So you are selling the leaf mold?
I am retired, but have built a 600 sq.ft. greenhouse. I sell plants at our local farmer's market. I also am pioneering sustainable and survivalist nursery production...like how to grow plants without Canadian Peat or fancy bagged and imported potting mixes. So what can I find for potting mix locally? The two main ingredients I can find are manures and leaves. Most all the manures I've found here are contaminated by Grazon. I did recently find for the first time in 5 years a small source of great horse manure. The leaves I pick up from bags set out for the landfill around town. Leaves take three years to decompose (mold) in this climate. I am not into just shredding them, but don't want to totally discount that as a practice. Leaf mold is full of healthful micro-organisms.