The study, cleverly titled, "Men set their own cites high: Gender and self-citation across fields and over time," found that a shocking 10% of all scholarly citations were done by authors citing their own work. Less shockingly, the majority of authors doing this are men.
The Washington Post points out that there's "nothing inherently shady about this practice," especially for experts in a particularly niche subject who sometimes have no choice but to cite earlier work. But the disparity in the practice between genders is definitely intriguing.
After looking into some 1.5 million articles published between 1779 and 2011, men were found to be 56% more likely to self-cite than women. And it wasn't merely due to an 18th century lack of female scholars. The percentage of self-citing by men actually increased to 70% more than women in the last two decades.