SCImago Journal Rank (SJR) indicators are released annually at Scimago Labs www.scimagojr.com (free). The underlying data come from Scopus.
The SJR indicator is inspired by Google's PageRank algorithm. A journal's SJR indicator is a measure of the number of citations received by its articles considering the importance of the journals where those citations came from. It is intended to measure journal prestige as opposed to journal popularity.
Calculation of the SJR measure has been modified; average SJR is now equal to 1, which means that journals with SJRs higher than 1 are more prestigious than average.