In recent years, insurance companies, pension funds, and other institutional investors have begun, with increasing frequency, to commit funds to the residential mortgage market, a market previously dominated by individuals and thrift institutions.

• The investment vehicle is a security known as a "mortgage pass-through certificate," which represents an ownership interest in a pool of mortgages and the resultant cash flow that derives from those mortgages.

• The entity that services the mortgages, often a thrift or mortgage banker, "passes through" mortgage payments, typically on a monthly basis, to certificate holders at a specialized "pass through" rate."