By going through some 34 million papers published in peer-reviewed journals and conference proceedings between 1996 and 2015, the Economist found that the average number of authors per paper rose in that time period from 3.2 to 4.4. This, the magazine adds, actually works out to a decrease in productivity as it says researchers are teaming up with co-authors to break up what would have been one paper into two or more — what it calls "minimum publishable units" — now that another researcher is on board.
Part of the cause in this increase in total number of authors is guest authorships, in which research institute directors or other bigwigs are added to the author list, the Economist says. It notes that that results in some researchers producing an unrealistically number of papers: the top 100 most prolific researchers in medicine in the US for 2013 through 2015 had an average of 180 papers a year.
Another cause, it says, is the rise of enormous research teams in fields like physics and genomics. It notes that a paper on the Drosophila genome had more than a thousand co-authors. "Such studies are paragons of scientific collaboration and the exact opposite of creating minimum publishable units," the Economist says. "But they list as authors people who have contributed only marginally to the success of the project — roles that, in the past, were simply acknowledged in a thanks-to-all sentence but are now the bricks from which careers may be built."