What are margin calls? The term has been bandied about lately as being one of the reasons for the steep declines in the market. Basically, it’s when depositor’s margin account at a brokerage falls below minimum levels and the brokerage tells the depositor to either deposit more money or they have to sell off some of their holdings. And a spate of selling drives down stock prices because as supply increases, prices drop. But why are there margin accounts and why are brokerages making margin calls in the first place? Marketplace’s ever-salubrious Paddy Hirsch explains with girl scouts, girl scout cookies, a whiteboard, dry-erase markers, and stick figures, in the video inside…