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Highlights
- Happens when a security's price rises with interest rate increases.
- Common in mortgage-backed securities (MBS) due to prepayment behavior.
- Contradicts traditional bond pricing dynamics.
Negative duration is a financial phenomenon in which the price of a security, particularly a mortgage-backed security (MBS), moves in the same direction as interest rates. This behavior is contrary to the typical relationship observed in traditional fixed-income securities, where bond prices fall when interest rates rise and vice versa.
The unique behavior seen in negative duration arises mainly in MBS due to the embedded option for borrowers to prepay their mortgages. When interest rates rise, homeowners are less likely to refinance or prepay their loans. As a result, the expected cash flows from the MBS extend further into the future, increasing the security's average duration and price sensitivity. However, the market may interpret this extension risk as an improvement in yield consistency, causing prices to rise slightly alongside interest rates under certain conditions.
Conversely, when interest rates fall, prepayments increase as homeowners refinance, reducing the duration and the expected return from the MBS. This causes prices to drop, defying the normal inverse relationship between bond prices and interest rates. These dynamics make MBS and other instruments with embedded options particularly complex to manage from a risk and duration perspective.
Conclusion
Negative duration highlights the intricate behavior of securities like MBS that contain embedded options. It challenges conventional bond valuation principles and underscores the importance of understanding prepayment risks and interest rate sensitivity in structured financial products.
