[brewer12345]

GNMAs are backed by Uncle Sam. As such, they effectively have no credit risk. What might be a source of risk is interest rate risk. If the market is bad, homeowners would likely not pay down their loans as fast, so you would have a loger duration than expected. If the market is really bad, there will be a lot of borrower defaults, which Ginnie would make good with cash, so you'd have a shorter duration than expected.