My favorite marketing demographic is the "14-49" age group, which was just made up by the CEO of some tv network in my country because that happened to be the group where they had the biggest viewer share. He basically looked at the numbers, retroactively constructed a demographic that would make his network look like the best advertising space in the entire country and then used every opportunity to claim that 14-49 is the most relevant target demo for advertising. And people actualy believed it for 20 years until he retired and told everybody he had been bullshitting them all the time.