...is very, very difficult. I want to know, for pretty much every era in history, an approximate estimate of the amount of information in circulation at that period. It doesn't have to be in terabytes or any definite unit, but I do need to know how much information one era contains relative to another, as in, how many times more knowledge is stored in current society than was stored in the world during the 1500's? During the dark ages? Right now I'm using a fairly arbitrarily defined function of world population, advancement of computers, and number of books in circulation. Any insights on how to more accurately define this function would be appreciated.