Interestingly, the study also found that men have more social contacts than women up until age 39. But, after age 39 women have more social contacts. In response to this finding, researchers told The Washington Post that women may be better at nurturing relationships with extended family members as they move into their 40's, saying, "The difference between the sexes seems to be primarily owing to the more frequent interactions by the females with their adult children and the children’s spouses. Also, females probably interact with their own close family members (e.g. keeping grandparents updated on the children’s activities) and the new in-laws created by their children’s marital arrangements more than males do."
Of course, this is only one study that looked only at phone calls, and should therefore not be taken as 100% solid fact. But, it's definitely reason enough to justify throwing a party this weekend with all your twenty-something friends.