The Source Normalized Impact per Paper (SNIP) indicator, created by Henk Moed, corrects for differences in citation patterns among disciplines. A journal's SNIP = (citation count per paper)/(citation potential within its field).
Calculation of the SNIP measure was modified in 2012; average SNIP is now equal to 1, which means that journals with SNIPs higher than 1 are better than average for their discipline.