Related to this is scientometrics, the science of science. It grew out of bibliometrics, the science of books and research papers. Others have observed a rate

Related to this is scientometrics, the science of science. It grew out of bibliometrics, the science of books and research papers. Others have observed a rate of decay (e.g. how long does it take for knowledge/facts within a discipline to change or be overturned) and attempted to quantify it for various disciplines. It's interesting to see how slow/fast facts in Medicine change versus philosophy versus religion. A nice read about this topic is a book by Samuel Arbesman, "The Half-Life of Facts".