In the context of Quantopian, is there any way to estimate money flows? For example, during the 2007-2008 financial crisis, I figure that money was flowing quickly out of stocks and into more secure investments. As the market has recovered, money has been flowing back into the market, right? I'd like to write an algorithm that would illustrate the relative flow in and out of the market, over the 2007-2013 time frame. Any guidance?