(redirected from biological half-life)
Also found in: Dictionary, Thesaurus, Medical, Encyclopedia, Wikipedia.


Copyright © 2012, Campbell R. Harvey. All Rights Reserved.

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.
Farlex Financial Dictionary. © 2012 Farlex, Inc. All Rights Reserved


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.
Wall Street Words: An A to Z Guide to Investment Terms for Today's Investor by David L. Scott. Copyright © 2003 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. All rights reserved.
Mentioned in ?
References in periodicals archive ?
According to the biological half-life in brain tissue, it is probably around 1 year; it is generally proposed that manganese is eliminated from the human central nervous system for a long period and at very slow rate [31].
where [C.sub.b] is the initial amount absorbed by an organic system, t is measured in years, and I is the biological half-life parameter such that 0.054757 [less than or equal to] l [less than or equal to] 0.164271.
Although only 3 infants had detectable antibody titers at 6 months of age, our study estimates the biological half-life of EV71 maternal antibodies to be 42 days, similar to the half-lives of antibodies to other pathogens calculated by using longitudinal analysis (1; M.-S.
Cadmium is a cumulative toxicant, with a biological half-life of [is greater than] 10 years in humans [12].
PolyXen is designed to improve the stability, biological half-life and immunologic characteristics of therapeutic proteins naturally.