Why is the freezer compartment colder at the top of a fridge?

[gamecube999]

Can somebody give me a detailed explanation of why the top compartment of a fridge is usually lower than that of the lower compartment?

I am thinking that because heat rises, so the heat flows from high energy (lower compartment) to low energy (top compartment)?

 

[russ_watters]

Because they dump more cold air into a smaller space...?

 

[TVP45]

It's the location of the coil and the vents.

 

[Loren Booda]

Please restate your question. Side-by side refrigerators, I recall, are least efficient (or is that more expensive?) Whether the freezer compartment on top or on bottom is more efficient depends on which realizes the smoother gradient of heat. The floor is more readily insulating than any other side, and the heat rises, two good reasons to have the freezer on the bottom, if it weren't for my darn back!