GNMA is the rare fund that focuses exclusively on mortgage-backed pass-through securities (MBS) issued by Government National Mortgage Association (GNMA, or Ginnie Mae), with maturities of 30 or 15 years. As a result, it ends to have a higher yield at the cost of more interest rate risk. The Underlying Index includes securities with a weighted average maturity of at least one year and have USD 1 billion or more of outstanding face value. These securities undergoes a monthly reconstitution. GNMA uses a representative sampling indexing strategy.