This is one of the most common ALM-related questions. Unfortunately, there is no single number that is appropriate for all lenders. The answer varies from one institution to another and depends on the interaction of a variety of factors including asset-related offsets such as a short investment portfolio and the amount of ARMs and HELOCs.  The amount of capital and the characteristics of the funding on the deposit side also play a major role in determining the amount of such loans that may be held.  A large certificate program, for example, with a long average maturity is risk-reducing on the one hand whereas a small program coupled with a very large money market account may reduce the amount of mortgage loans that may be held. Similarly, the use of longer term FHLB borrowings can be used to fund the longer portion of a pool of mortgage loans. The nature and size of the share draft program is also a determining factor because these funds behave as if they are longer term deposits and often pay no interest even when market rates increase