Now it is official. Men really are more narcissistic than women, according to a massive American study which analysed three decades of data from more than 475,000 people.
Researchers concluded that men had a greater senses of entitlement, making them more likely to exploit others.
The findings were consistent across multiple age groups and generations, said the study's authors at the University at Buffalo School of Management.
However, men can take comfort in one conclusion from the study - narcissism may also have some positive effects.
"Narcissism is associated with various interpersonal dysfunctions, including an inability to maintain healthy long-term relationships, unethical behaviour and aggression," said Emily Grijalva, assistant professor of organisation and human resources, and the paper's lead author.
"At the same time, narcissism is shown to boost self-esteem, emotional stability and the tendency to emerge as a leader."
They sifted through more than 355 journal articles, dissertations, manuscripts and technical manuals, and studied gender differences in what they described as the three aspects of narcissism: leadership/authority, grandiosity/exhibitionism and entitlement.
It meant examining reactions to statements such as, "If I ruled the world, it would be a much better place," and "I know that I am good because everyone keeps telling me so."
They found the widest gap in entitlement, suggesting that men were more likely than women to exploit others and feel entitled to certain privileges.
The difference narrowed when it came to vanity, which may explain why some women feel the need to clog Twitter and Facebook with countless pouting selfies.
The results will be published in the forthcoming Psychological Bulletin journal.