A highly effective backup system would have duplicate copies of every file and program that were immediately accessible whenever a "Data Loss Event" was noticed. However, in most situations, there is an inverse correlation between the value of a unit of data and the length of time it takes to notice the loss of that data. Taking this into consideration, many backup strategies decrease the granularity of restorability as the time increases since the potential "Data Loss Event". By this logic, recovery from recent "Data Loss Events" is easier and more complete than recovery from "Data Loss Events" that happened further in the past.