Forward Pricing

A casual walkthrough of forward pricing for zero coupon bonds — showing how today's spot rates imply a locked-in future price, and why realized rates rarely match what we expected.

Feels like I’m basically re-running the Implied forward rate stuff I already covered before… honestly I wanted to just skip this whole part lol. But it’s in the book, so — let’s (once again) take a quick peek.

At the current point $T=0$, all kinds of zero coupon rates are floating around out there in the market. And I mentioned that the forward rate you compute from those spot rates is what we call the implied forward rate.

So at $T=0$, a 2-year zero coupon bond with $1 face value is going for

Equation from the original notes

That’s the price it’s trading at, right?

Now if you promise today to sell that same bond one year from now — what price would be the rational one to lock in?

The price below is exactly that rational locked-in number — the Market Fair Value. (It’s the delivery price today’s curve implies, with no arbitrage; it’s not a forecast that the bond will actually trade at that price a year from now.)

Equation from the original notes

And honestly… that’s the entire Forward Pricing chapter.

But OK — when $T=1$ actually rolls around, is the 1-year yield as of $T=1$ — let’s call it $s_1'$ — going to match the $_1f_1$ we expected (computed) back in the past??

Obviously not — not exactly, anyway. Market rates don’t sit still. There’d be trades happening between people who think $s_1'$ will end up higher than the $_1f_1$ implied at $t=0$, and people betting it’ll come in lower.

Equation from the original notes

Now let’s look at the same thing but just stretch the timeline a bit:

Equation from the original notes

At the current point $T=0$, a zero coupon bond with a 5-year maturity

Equation from the original notes

is trading at this price. If you enter a contract (forward) to buy/sell this bond at $T=2$, the Market Fair Value comes out to

Equation from the original notes

That’s literally all it’s saying bro. Forward Pricing has, like… genuinely nothing to it. T_T

Equation from the original notes

The Forward Rate Model

OK, this time — instead of the Forward Pricing we just did, we’re talking about measuring the “Rate” itself. And in the book it’s written out with this kind of formula:

Equation from the original notes

But if we just slap it on a timeline and rewrite it in our own notation,

Equation from the original notes

Wait — it’s literally the same thing lol! The only difference is we’re writing it in terms of yield instead of price.

Done!

Equation from the original notes

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