Journal level metrics look at numeric measures of performance of all articles within a journal within a set period of time, transform the numbers using mathematical formulas, and rank journals using the resulting integers.
Each product or group counts different metrics as performance; uses different formulas; and count different journals. Many of the journal impact measurements have been developed by publishing companies and so cannot be used to assess journals owned by other publishers. This can lead to many different numbers and rankings: a journal may rank highly in one system, and not be ranked at all in another. Consider using several journal level metrics to fully understand the role and impact of this journal.
There is significant controversy and discussion in various academic communities about which Journal Impact methods are most accurate, and if journal impact can be used to represent individual researcher impact, article impact, or institutional impact. Read the San Francisco Declaration on Research Assessment, a statement written by publishers and editors, and endorsed by over 100 universities and funding agencies, for a summary and explanation of controversies about journal level metrics. Explore this guide for commonly used metrics for assessing journal impact, and contact the USC Libraries with questions about other metrics.