Impact factors refer to the number of times an article in a journal has been cited. It determines the journal's importance and ranking. The higher a journal's impact factor the greater its importance in a specific field.
Calculating Impact Factor
A = the number of times articles published in 2008 and 2009 were cited by indexed journals during 2010.
B = the total number of "citable items" published in 2008 and 2009.
Critically evaluate and compare journals in the sciences and social sciences using citation data from over 7,500 scholarly and technical journals. Use JCR to find the most frequently cited journals, and measure research influence through impact factor, aggregate impact factor, the aggregate immediacy index, aggregated cited half-life, and the number of articles in each category. Full name of the database is Incites Journal Citation Reports.