A net interest margin (NIM) securitization is essentially an interest only (IO) strip, with its cash flow derived from a transaction9s net interest proceeds as well as from interest rate caps, corridors, and swaps, and, for most RMBS NIMs, prepayment penalty charges. Several factors can impact the amount of residual cash flow available to service NIM liabilities. These factors include collateral losses, the timing of losses, prepayment speeds, the interest rate environment, and structural features. NIM performance is heavily dependent on collateral performance in the early life of the transaction. Consequently, performance can be particularly vulnerable to sharp downturns in more credit sensitive sectors of the housing market.