Introduction

The number of publications has been used as a form of recognition in scientific research since the late 19th century, concurrent with the development of scientific publishing (Csiszar, 2018). In many disciplines, the number of publications is an important indicator of researchers’ productivity and performance; they are sometimes used as a proxy in research assessment involved in the process of recruitment, tenure and promotion and grant applications. The phrase ‘publish or perish’ has been used to describe the significance of publications in research culture. Eugene Garfield's invention of the Journal Impact Factor (JIF) creates another ‘measure’ in research evaluation: citations. The rationale is that the more an article is cited, the more impactful it is. Citation-based metrics are then used to assess the quality of research in the STEM disciplines and are currently used in tools for benchmarking and tracking research performance of individuals, research groups and institutions. In this chapter, the term ‘research metrics’ refers to metrics generally used in research evaluation, including the number of publications and citations, as well as citation-based metrics and indicators.

Citation indexes were first conceptualised and invented as a bibliographic tool for facilitating information access and retrieval. In his seminal paper, Eugene Garfield envisions ‘a bibliographic system for science literature that can eliminate the uncritical citation of fraudulent, incomplete, or obsolete data by making it possible for the conscientious scholar to be aware of criticisms of earlier papers’ (Garfield, 1955, 108). Garfield founded the Institute for Scientific Information (ISI) and created the Science Citation Index (SCI). In 1972, he published the article, ‘Citation Analysis as a Tool in Journal Evaluation’ (Garfield, 1972), which illustrates the use of citation counts to assist collection development. Over time, publications in highimpact journals become perceived as more significant and the JIF is used not only for evaluating journals, but also individuals, notwithstanding that the JIF is a journal-level metric.

Today, citation-based metrics are often used as indicators of research quality and impact. These metrics, however, are based on different data sources and methods and many are not appropriate for evaluating individuals’ research performance. Hence, these differences must be understood when used in journal evaluation and research assessments.