I think that it can be safely assumed that some muscle growth does occur during the day, but I've never been able to find out how much more occurs during sleep. Its always bugged me because it seems like it's something that should be more or less known.
As for
why anyone would want to know, if I had some general statistics it might change the way I eat, not to mention the pure curiosity of it. What if the ratio is 80% asleep, 20% awake? Wouldnt that make you want to load up protien in the two hours or so before bed? And if daytime growth is comperable to sleep growth?
Its not as if im trying to say that this bit of info is absolutely critical, but it should at least tweak your curiosity a little.
The implication of course is that protien cannot be stored for later use in muscle repair.. but you knew that

heres an interesting article, doesnt answer my question though
How Do Muscles Grow?