The 20 year rule.

History is just one of the many social sciences, but it's not always easy to draw a line between them. That's why you have economic sociologists and ethnohistorians. Technically, yes, you could ask every single question submitted here at /r/asksocialscience as well. But if you’re like me and study the past, you don’t want to have to filter through questions on economics and political science and gender studies to get to history and/or archaeology. Our 20 year rule is a way to specialize, focusing questions and attracting the right responders. DotA, Pokemon, and CoD are video games, but that doesn't exclude them from having their own sub separate from r/gaming.