For Bank of America (NYSE:BAC) and Wells Fargo (NYSE:WFC), or even the government-sponsored entities such as Freddie Mac (OTC:FMCC), mortgage lending is big business. 

It's true across the industry, for institutions large or small. And that's why the current supply and demand outlook for good-quality mortgage loans is scary. 

In the following video, Fool contributor Jay Jenkins walks us through a supply-and-demand chart he created from recently released data from the Federal Reserve. As he demonstrates, while supply may be stable, the sharp rise in interest rates over the past several months has done some serious damage to the demand side.