Big banks like Bank of America (NYSE:BAC) and Citigroup (NYSE:C) have got into trouble in the past when interest rates rose and they were unprepared for the shift due to an inadequate duration of their portfolio. With interest rates at record lows and many believing they can only go up from here, many banks are lending out less of their deposits in preparation. 

Fool.com financial analyst Matt Koppenheffer explains this dynamic today and how it could impact big banks going forward.