In academia, article citations like these are a marker of authority and influence: If your work gets cited by others hundreds of times, that's a good indicator that you're making a mark on your field. Universities often factor in citation counts when making decisions about hiring, tenure and pay.
As it turns out, academics have a handy tool at their disposal for juicing their citation counts: They cite themselves. There's nothing inherently shady about this practice. If you're an expert in a relatively obscure field like ant taxonomy, you're probably going to need to cite your previous work because few people people are doing similar work.
So Molly M. King and her colleagues at Stanford University, the University of Washington and New York University set out to find how often this so-called "self-citation" happens. They did so by examining a massive database of academic work: 1.5 million research papers in JSTOR, a digital library of academic books and papers published between 1779 and 2011.
What they found, first of all, is that self-citation represents a significant chunk of all academic citations. There were 8.2 million citations contained in the 1.5 million papers they studied. Nearly 775,000 of those citations, or about 10 percent of them, were of authors citing their own work.
For some individuals, the share of self-citations was much higher. They give an example of one "prominent scholar" (they don't name names, because academia is a small world) who has received more than 7,000 citations of his work. More than a fifth of those citations came from himself.
But more strikingly, King and her colleagues found a huge difference in self-citation patterns between men and women. "Over the years between 1779-2011, men cite their own papers 56% more than women do," they found. And in recent decades, men have stepped up their self-citation game relative to women: "In the last two decades of our data, men self-cite 70 percent more than women."
This self-citation gap held true across every major academic field the authors studied, including biology, sociology, philosophy and law. In a footnote, the paper's authors — three women and two men — dryly note that the pattern holds among themselves as well: "The men authors of this paper cite themselves at nearly three times the average rate of the women authors."
There's also the simple fact that men tend to publish more, particularly early on in their careers — a time when many female academics might be grappling with the challenges of balancing career with maternity leave. If you've published more papers, you have more chances for citing your own work.
Regardless of the underlying mechanism, the self-citation disparity has a real-world impact on female academics' careers. Academics are more likely to cite papers that are already well-cited, so citing yourself means more citations from others. And more citations means better career-advancement opportunities.
This phenomenon probably contributes to women's continued under-representation on college faculties. Women have earned at least half of all bachelor's degrees in science and engineering fields since the late 1990s, according to the National Science Foundation, but as of 2013, they represent fewer than a quarter of university faculty members in those fields.