All four methods are available to rank authors. The first two methods are available to rank universities.
Normal count: Every coauthor of a paper receives a score of 1. His/her school of affiliation receives a maximum score of 1 for each paper, even if there are multiple authors from the same school.
Adjusted count: Single-authored papers result in the school of affiliation and author being credited with a score of 1. If there are multiple authors from different schools, each school gets a score of p/n, where p is the number of authors from the same school and n is the total number of authors on the paper; and each author gets a score (credit) of 1/n. If an author lists multiple affiliations, each of the schools that author is affiliated with gets a corresponding scaled score. For example, if one of the n authors lists m affiliations, each school that author is affiliated with gets a score of 1/nm.
Weighted count: Papers are given a reduced weight based on the number of authors. 1 point is given to single-authored papers, 0.7 point is given to papers with two authors, 0.5 point is given to papers with three authors, and 0.3 point is given to papers with four or more authors.
Straight count: Only the first author is given credit for a paper.
Chua, C., Cao, L., Cousins, K., and Straub, D. “Measuring Researcher-Production in Information Systems,” Journal of the Association for Information Systems (3), 2002, 145-215.