  In some research evaluation systems, credit awarded to an article depends on
the number of co-authors on the article with total credit to the article
increasing with the number of co-authors. There are many examples of such
evaluation systems (e.g., the United States National Research Council
evaluation of graduate programs gave full credit to each co-author). Such
credit systems run the risk of encouraging ghost or honorary authorships. In a
recent article, Antonio Osorio and Lutz Bornmann (2019) propose a scheme to
discourage ghost authorships but increase the total credit to a paper when
co-authorships increase. It is shown that if articles are valued more highly as
the number of co-authorships increases, then there are opportunities to
increase credit by mutually agreeing to add each other as authors. Unrelated
authors of unrelated papers may all benefit by expanding their co-author list.
I call this phenomena arbitrage--a term borrowed from economics and
finance--since the content of the articles do not change, but the value
increases by moving to a "market" of more co-authors where articles are valued
differently.
