It is pretty easy to "predict" the past, you know...
Only if you don't have to calculate the past. Since we weren't around 2000 years ago and since the backup technology was much more primitive then, we don't really have the numbers for 2000 years ago. That means that we have to calculate or, "predict" if you wish, the numbers. I believe that 2000 years ago, during the reign of Pontius Pilate and his friend Biggus, we only had an early version of NetBackup and LTO 1 tape which cannot be read any more. GPS records from those days are also not very reliable. So we don't have the records and we do need to "predict the past", as you've succinctly put it.
"Ask not what A Group of Employees can do for you. But ask what can All Employees do for A Group of Employees." -- Mike Dennison