The paper’s authors reviewed data from 2008, then compared it to the results of a previous study conducted in 1996. Davis summarizes their findings.
In 2008, self-reports of ghost authorship was 7.9%, down from 11.5% in 1996. In comparison, rates of honorary authorship remained statistically similar over time (17.6% in 2008 versus 19.3% in 1996). Prevalence of honorary authorship in research articles was higher in 2008 than in 1996, but lower for review articles and editorials.
Surprisingly, journals that require authors to detail their contributions showed no difference from journals without such author requirements.
Honorary authorship is the practice of granting authorship to often-powerful individuals (deans and the like) who may not have had a direct role in the study.
While the results may appear encouraging, Davis does provide a cautionary note.
While this study was beautifully and rigorously executed — with a response rate of over 70% — the researchers acknowledge that respondents may not be forthright with reporting inappropriate authorship practices, especially considering the social stigma against ghost authorship. Indeed, a study of members of the American Medical Writers Association and European Medical Writers Association put the incidence of ghostwriting at 42% for 2008, down from 62% in 2005. If the incidence of ghost writing is truly declining, it still has a long way to go.