A model risk manager is reviewing the output from a prepayment model for a portfolio of recently issued government agency-backed MBS, where balances on underlying mortgages are still relatively high. The model uses a scenario in which interest rates are relatively high and do not change, the equity market declines by 20%, demand for housing does not change, and unemployment increases by 2%. Based upon those inputs, the model indicates that prepayments will increase significantly over the next 6 to 18 months. Assuming the agency backing the MBS remains solvent, which of the following provides the most likely explanation for the increase in prepayments in the model scenario?