The financial crisis in 2007-2008 caused big problems in the economy. Banks lost a lot of money because of bad loans from people not paying their mortgages. This led to a big drop in the stock market. The researchers in this paper want to understand why this happened. They found that the losses in the mortgage market spread to other parts of the economy, causing a lot of problems like banks not having enough money and people not being able to pay their debts. This made the government step in to help out.