term structure of interest rates (in ALM)

Lending money for one year and lending it for thirty years usually earn different rates. The relationship between the length of an investment and the interest rate it commands is the term structure of interest rates; plot rate against term and you get the familiar yield curve. Most days it slopes gently upward — longer money pays a bit more — but it can flatten or even invert (short rates above long rates), a pattern that has often preceded recessions.

We met this idea in interest theory; here we look at it through the lens of asset-liability management, where it stops being a picture and becomes a working tool. An insurer's liabilities are spread across many future dates. Each of those dates has its own market interest rate. Discounting next year's claim at the 1-year rate and a claim 30 years out at the 30-year rate gives a market-consistent value of the whole liability, and it tells you which maturities of bonds will best back which parts of the obligation. A single flat rate would blur all of this together and quietly misstate the value when the curve is steep.

Why it matters in practice: the entire job of matching assets to liabilities is conducted along the curve. If long rates rise and short rates do not (the curve steepens), a long liability becomes cheaper to fund while a portfolio of short bonds barely moves — so the mismatch you care about is not just the level of rates but the shape of the curve. Modern valuation standards build the discount rate straight from the observed curve rather than from one chosen number, precisely so that the value of promises tracks the market that will ultimately fund them.