The "impact factor" is a measure developed from data collected from the Web of Science. It is often used as a measure of the importance or impact of a journal's articles on known knowledge.
"The impact factor reflects the number of citations of a journal’s material in the preceding two-year period divided by the number of citable materials (source items) published by that same journal within the same period." (Kurmis, 2003)
The impact factor has received some criticism that the scholarly community has overestimated its importance and is being misused. Other citation metrics have also been developed, including the H-index, the Eigenfactor, and SCImago Journal Rank.
