What it means
Governments borrow by selling bonds at auction, and the 30-year maturity sits at the far end of that range. Because the money is committed for three decades, the yield reflects what investors demand for very long exposure to inflation, policy changes and interest rate movements.
For a business audience the number matters even if the company never buys one. Long-dated mortgage rates, corporate bond pricing, pension liability valuations and the discount rates used in long-horizon investment appraisals all take their cue from long government yields.
The relationship between price and yield is inverse, and at long maturities it is powerful. If market yields rise, the price of an existing 30-year bond falls sharply, because its fixed coupon is now less attractive than the coupon on newly issued bonds; this sensitivity is measured by duration.
The return on the bond can be described in several ways, and mixing them up causes most of the confusion. The coupon rate is the fixed interest printed on the bond as a percentage of face value, while the current yield and the yield to maturity describe what an investor actually earns given the market price paid.
Comparing the 30-year yield with shorter maturities gives the shape of the yield curve, which analysts read as a signal about expected growth and inflation. Issuance of this maturity has been suspended and restored in the past, so the auction calendar is a policy decision of the Treasury rather than a permanent fixture.
In practice
Real-world examples.
Example
An actuary values pension promises that run 30 years into the future and uses long government yields as the discount rate. A fall of half a percentage point in the 30-year yield raises the measured liability by millions and pushes the scheme's funding level down, with no change in the benefits promised.
Example
A corporate treasurer planning a 30-year infrastructure bond watches the long Treasury yield as the floor on his cost of funds. The company's own issue will price at that yield plus a credit spread reflecting its risk, so a quiet week at the long end is a good week to come to market.
Example
An insurer backs long-dated annuity promises with 30-Year Treasuries so that assets and liabilities move together. When yields jump, the bonds fall in value, but the present value of the promises they fund falls too, which is the point of the match.
Formula
Calculation
Annual coupon interest = face value x coupon rate. Current yield = annual coupon interest / market price paid.
An investor buys a 30-Year Treasury with a face value of $100,000 and a coupon rate of 4%. The annual coupon interest is $100,000 x 4% = $4,000, received as two instalments of $2,000 each. If the bond is bought in the market for $90,000 rather than at face value, the current yield is $4,000 / $90,000 = 4.44%. Bought instead at $110,000, the same bond gives $4,000 / $110,000 = 3.64%, which shows plainly how a higher price means a lower yield on identical cash flows.Case study
Seen in the real world.
Northbank Mutual Assurance is a fictional insurer used here as an illustrative example. In the story it held $600 million of 30-Year Treasuries with an average coupon of 4% against annuity promises running out to 2055.
When long yields rose by one percentage point in the illustrative scenario, the market value of those bonds fell by well over $100 million, and the finance director faced an uncomfortable board meeting. The chief actuary showed that the value of the annuity promises had fallen by a similar amount, so the funding position was broadly unchanged and no assets needed to be sold at a loss.
The fictional lesson is that a long bond's price swing only becomes a real loss if the holder is forced to sell. Northbank's deliberate match of maturities was what turned a frightening headline number into a non-event.
Watch out
Common mistakes.
- Reading the coupon rate as the return an investor will earn, when the actual return depends entirely on the price paid for the bond.
- Describing long government bonds as risk free in every sense; the risk of default is very low, but price swings and inflation over 30 years are substantial risks.
- Assuming a rise in short-term policy rates moves the 30-year yield by the same amount, when the long end frequently moves by less or even in the other direction.
Questions
People also ask.
Why does the price fall when yields rise?
Newly issued bonds pay more, so an older bond with a fixed coupon must be cheaper for a buyer to earn a competitive return, and 30 years of fixed payments makes that price adjustment large.
How is the 30-Year Treasury different from a 30-year mortgage rate?
One is what the government pays to borrow, the other is what a household pays, and the gap between them covers credit risk, servicing costs and the risk of early repayment.
Can an investor sell before maturity?
Yes, the market is deeply liquid and a sale settles quickly, but it happens at the prevailing price, which may be well above or below the amount originally paid.
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