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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.


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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More than six million tuned in on Saturday night to watch Philip play mysterious ex-CIA agent Rupert, now a crusader in a war between humans and the halflife in modern-day London.
In lung tumor tissue, the effective halflife of the metabolite was increased from 15 hours with irinotecan to 6 days with NKTR-102.
Vampire uses the same technology as Halflife 2 so the games shimmers with the same loveliness.
Because of the shorter biological halflife of BNP compared with NTproBNP (6), we hypothesized that BNP would show a faster response to hemodynamic improvement during intravenous levosimendan therapy.
Performance tested on HalfLife 2: Day of Defeat (anzio level) at settings of 1600x1200 4xAA/8xAF shows GeForce 7900 GT scoring 54 fps vs GeForce 6800 GT scoring 26.
But none - and I mean NONE - has been more eagerly awaited than HalfLife 2.