Measuring impact in research evaluations
Governments all over the world are contemplating the question of where they should distribute public money (to education or to defence, for example). Distribution of money over a number of different areas always makes an issue, implicitly or explicitly, of the impact which can be achieved with investment in any one of them. Science is also affected by this governmental interest in impact; the issue is not only the impact of research on research itself, but on other areas of society. Citations are traditionally used to measure the impact of research on research. It is as yet unclear how the impact of research on other areas of society can be measured. It appears that alternative metrics (altmetrics, such as Twitter counts) might play a key role in this. This paper is concerned with the measurement of citation impact and societal impact, and looks at the basis, the effects and the problems of impact measurement.