1. A computerized method for calculating a normalized activity score value to rank an identified document, the method comprising: identifying a stored document; determining a number of times the identified document was cited in a subject matter community of the identified document; determining a probability distribution that individual documents within the subject matter community are cited a variable number of times by other individual documents in the subject matter community; calculating a probability function by performing a regression on the probability distribution; calculating the activity score value according to an activity score function formulated as an inverse of the probability function such that the activity score function is defined by: Score ⁡ ( x ) = k ( a · x α + 1 ) p , wherein: Score(x) is the activity score value, k and p are constants, x is the number of documents citing the identified document, and a and α are learned from the regression on the probability distribution; and the activity score function is such that the activity score value is calculated according to a probability that the individual document in the subject matter community is cited a number of times greater than or equal to the number of times the identified document was cited in the subject matter community; weighting the activity score value by an age of the identified document; and storing in computer memory a ranking of the identified document based on the activity score value.