5. A system according to claim 4 , wherein the similarity measures comprise an amount of potential overlap in core interests of the home community and the frontier communities of the plurality of the frontier evergreen indexes.
4. A system according to claim 1 , further comprising: a subject area evaluation module configured to compare the topically-limited subject areas of the home evergreen index to the respective topically-limited subject areas for a plurality of the frontier evergreen indexes; a similarity evaluation module configured to determine similarity measures of the respective subject areas of the home evergreen index and the plurality of the frontier evergreen indexes; and a frontier candidate selection module configured to select the at least one frontier evergreen index from the plurality of the frontier evergreen indexes based on the similarity measures meeting at least one of a minimum threshold or up to a fixed number of the articles of the digital information.