# half-life

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## Half Life

In a pool of mortgages underlying a mortgage-backed security, the length of time it takes for half the aggregate principal to be repaid. A half life is normally about 12 years, but this may vary depending on how often homeowners refinance their mortgages (which pays off all principal at once). Half lives are calculated for mortgage-backed securities issued or guaranteed by Freddie Mac, Fannie Mae, and Ginnie Mae.

## Weighted Average Life

The amount of time for the principal on a loan or a mortgage to be paid off. The length of the weighted average life depends on the amount of principal paydowns and how often they are made. Once the WAL is calculated, one can determine how long it will take to pay off half of the remaining principal.

## half-life

The length of time before half the principal on a debt is expected to be repaid through amortization or sinking fund payments. For example, a 25-year bond issue may require the issuer to retire 5% of the beginning principal commencing 5 years after the issue date. Thus, the bond issue has a half-life of 5 years plus the number of years required to retire half the issue, or 15 years. Mortgage-backed securities often have a relatively short half-life because many homeowners pay off or refinance their mortgages early. Also called average life.
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Understanding the interaction between albumin and FcRn and the impact on albumin fusion half-life has enabled the engineering of this interaction with the potential to modulate albumin's half-life.
The half-life of DCD in soils was quantified using regression analysis by fitting the DCD concentration in the soil as a function of time to a first-order exponential model as follows (Kelliher et al.
This article presents the concept of half-life analysis of learning curves (Badiru, 2010), using the concept of growth and decay of learning in the acquisition environment.
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This technology is designed to improve the stability, biological half-life and immunologic characteristics of therapeutic proteins naturally.

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