The only factor MBS had in any of this, and it was relatively small, was compared to "normal" notes and bonds (govt or corp) the duration of mortgages extends i

The only factor MBS had in any of this, and it was relatively small, was compared to "normal" notes and bonds (govt or corp) the duration of mortgages extends in a risking rate environment due to fewer prepayments. So rather than say a 4% change for every 100bp move in interest rates, the MBS might change 4.5 or 5%.