80% of the citations come from about 20% of the journals cited, identifying a core list for a local journal collection.

-- (Chung, 2007)

Internationally, increasing emphasis is being placed on the measurable impact of research.  In Australia, factors behind this include:

• economic conditions and increasing competition for government funding
• development of ERA* which measures the academic excellence of research and the view that impact measures would complement this assessment
• general concern to improve the operation of the national innovation system
• need to demonstrate to the public that research funds are well-spent 

(Rymer, 2011)

Bibliometrics is a term that encompasses the range of statistical analysis related to publications and their authors. This data is used to develop research impact “profiles” for specific individuals, papers, journals and disciplines, institutions and countries.

Each measure has advantages and disadvantages, related to discipline characteristics, inclusiveness of the measures, and the accessibility of the data; and no single measure should be used in isolation.

*Excellence in Research for Australia (ERA) initiative 

Rymer, L. (2011). Measuring the impact of research - the context for metric development. In The Group of Eight (Ed.), Go8 Backgounder (Vol. 23). Turner, ACT.

A Google Scholar search will further reveal the merits and deficiencies of impact data for diverse disciplines.