your line of reasoning is only valid if every member posts their date of birth in their profile. random checking of 10 members reveals 6 out of 10 post theirs. so, 60% of 11,619 = 6,971 members post their dob. 6,971 divided by 365 days = 19 members per day. 40/19 = 210%
so, 40 is 'unusually' high than the average. i have done my math.