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What Is Single Monthly Mortality?

By Kristi Waterworth – Updated Jun 3, 2025 at 9:54AM

Key Points

  • Single monthly mortality helps gauge MBS investment health by tracking premature loan payoffs.
  • Initial fast prepayment phase of an MBS is now shorter than in the 1980s, impacting profits.
  • Calculate single monthly mortality by comparing expected vs. actual payments, expressed as a percentage.
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