This is a complicated topic, and it is important to understand that no single citation count methodology is perfect. Most citation counts rely on domestic law journal article citations, sometimes to the exclusion of interdisciplinary journals, foreign journals, books and book chapters. The more straightforward single author methodologies (i.e. as opposed to institutional methodologies, see supra) include HeinOnline Author Profiles, which provide citation counts, and Google Scholar Profiles which provide both citation counts and the author's h-index, determined by the author having n articles cited at least n times. For example, an author may have 6 articles, one of which has been cited 70 times, one cited 35 times, two cited five times, and two cited 3 times, thus giving the author a h-index of 4 because only 4 articles had been cited at least 4 times.
In addition to these, authors may wish to download and use the Publish or Perish software which pulls citation metrics from a variety of sources including Google Scholar and Web of Science. More information on this topic can be found in the resources listed below.
Institutional citation counts include the Scholarly Impact Score designed by Brian Leiter of Chicago Law School, and continued every 3 years by Gregory Sisk and his team at St. Thomas Law School (the Leiter-Sisk methodology). However, this Westlaw based method only computes scores for the top 99 law schools and is therefore limited to citations that appear in law journals. The score is computed over the past 5 years by taking the mean number of citations x2 plus the median number of citations, thus providing a weighted score which in turn can be used to produce an ordinal score for ranking purposes. A similar methodology has recently been used by Paul J. Heald and Ted Sichelman employing the HeinOnline and SSRN platforms. Results from that study largely confirmed the studies using the Leiter-Sisk methodology, however the latter study not only is limited to citations appearing in law journals it also only includes citations in those journals to works published in law journals (i.e. does not include books, book chapters, non-law journals, etc).
Attempts to include interdisciplinary scholarship produced by law faculty include a Web of Science based methodology devised by J.B Ruhl, Michael Vandenbergh and Sarah Dunaway from Vanderbilt University.
In February 2019, U.S. News announced it would publish a law faculty scholarly impact ranking in 2019 based on 5-year citation data from HeinOnline. In November 2020, U.S. News announced it would be publishing the ranking in 2021. In June 2021, U.S. News abandoned its effort to rank law faculty scholarly impact:
Publish or Perish is a software program that retrieves and analyzes academic citations. It uses a variety of data sources to obtain the raw citations, then analyzes these and presents a range of citation metrics, including the number of papers, total citations and the h-index.
The results are available on-screen and can also be copied to the Windows or macOS clipboard (for pasting into other applications) or saved to a variety of output formats (for future reference or further analysis). Publish or Perish includes a detailed help file with search tips and additional information about the citation metrics.