An indexing method for reducing storage requirements in the context of text communication analysis, the method comprising: - receiving a set of communications and a set of probability scores from a statistic generator, wherein each communication within the set of communications is assigned a corresponding probability score from the set of probability scores, wherein each probability score indicates a likelihood that the corresponding communication belongs to a particular classification mode, - sorting the communications within the set of communications based on the value of their corresponding probability scores from the set of probability scores, wherein, as a result of sorting, a sorted list of communications with corresponding probability scores is obtained, - dividing the sorted list into buckets, whereby each bucket initially includes a predetermined number of communications and its corresponding probability scores, wherein the buckets are separated by boundaries between the buckets, - determining a representative value for the probability score of each bucket, wherein the representative value is an approximation of the corresponding probability scores of the communications included in a bucket, - moving the boundaries between the buckets and, in response to moving boundaries, recalculating the representative value for the probability score of each bucket, wherein the steps of moving and recalculating are repeatedly performed until deviations of the corresponding probability scores of the communications within the buckets with respect to the representative value for the probability score of the buckets are equal to or less than a threshold, - assigning a bucket index to each of the communications, wherein the bucket index is representative of the bucket in which a respective communication is included, - storing (616, 618) only the assigned bucket index and the recalculated representative value for the probability scores of each bucket. - receiving a set of communications and a set of probability scores from a statistic generator, wherein each communication within the set of communications is assigned a corresponding probability score from the set of probability scores, wherein each probability score indicates a likelihood that the corresponding communication belongs to a particular classification mode, - sorting the communications within the set of communications based on the value of their corresponding probability scores from the set of probability scores, wherein, as a result of sorting, a sorted list of communications with corresponding probability scores is obtained, - dividing the sorted list into buckets, whereby each bucket initially includes a predetermined number of communications and its corresponding probability scores, wherein the buckets are separated by boundaries between the buckets, - determining a representative value for the probability score of each bucket, wherein the representative value is an approximation of the corresponding probability scores of the communications included in a bucket, - moving the boundaries between the buckets and, in response to moving boundaries, recalculating the representative value for the probability score of each bucket, wherein the steps of moving and recalculating are repeatedly performed until deviations of the corresponding probability scores of the communications within the buckets with respect to the representative value for the probability score of the buckets are equal to or less than a threshold, - assigning a bucket index to each of the communications, wherein the bucket index is representative of the bucket in which a respective communication is included, - storing (616, 618) only the assigned bucket index and the recalculated representative value for the probability scores of each bucket.