I realize that Google's algorithms are closely guarded secrets, but can anybody hazard a guess why, when I search for "NBA," the number of results sometimes varies by hundreds of millions from day to day.
Given the numbers are that large, there has to be a cut off at some point and it is unlikely to be an absolute value such as the number of references found. More likely it is a semi-arbitrary value such as search time or aging of links. That is not an uncommon practice when dealing with such a large number of data points otherwise a search might never terminate.
Even though these are big numbers the difference in the two values is less than 3%.
