Spot/forward rates method calc

Hi,

I’m a bit confused regarding the method of these two questions. Why do we in the first one just divide by spot rate and in the second we take spot rate x forward rate?

MODULE QUIZ 57.1

  1. If spot rates are 3.2% for one year, 3.4% for two years, and 3.5% for three years,
    the price of a $100,000 face value, 3-year, annual-pay bond with a coupon rate of
    4% is closest to:
    A. $101,420.
    B. $101,790.
    C. $108,230.
  2. Given the following spot and forward rates:
    Current 1-year spot rate is 5.5%.
    1-year forward rate one year from today is 7.63%.
    1-year forward rate two years from today is 12.18%.
    1-year forward rate three years from today is 15.5%.
    The value of a 4-year, 10% annual-pay, $1,000 par value bond is closest to:
    A. $870.
    B. $996.
    C. $1,009.

1.A 5.C
Kaplan page 85 Fixed Income book 4

Thanks so much!

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In #1, you have a series of cash flows that are basically spot. Therefore, all you have to do is discount year t’s cash flows by the t-year spot rate. Simple and easy!

In #2, you can either invest at the t year spot rate (which is NOT provided for t>1) or you can invest at the 1 year spot and reinvest at the forward rate for the next 3 years. These are just 2 different paths to get you to the same end result.

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Sorry Breadmaker but I don’t get why I in one case can just to CF/DF^N and in the other I can do CF/DF*DF without raising it to the number of years.

Let’s say you wanna invest $1,000 for 2 years. I have a 1 year spot rate handy, but I can’t give you a 2 year spot quote. However, to get you to the SAME END RESULT, I will take whatever accumulated balance you have at the end of year 1 and REINVEST at the forward rate.

End of year 1 AV = 1,000 x 1.055 = $1,055
End of year 2 AV = 1,055 x 1.0763 = $1,135.50

So if I need to pay a coupon at time 2, you would discount it using the SAME PATH you used to roll up the AV at time 2.

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I don’t really understand why but I guess I have to just memorize that when it comes to the case when it is both spots and future rates I just have to forget about N and just multiply them all together. When it is spot rates I just use them for the specific year and raise it to n. It feels like this whole test is a lot about just memorizing things.

You must raise the Discount Rate for a certain number of years because the spot rates given to you as annual rates.
If you invest $100 at a 2-year rate of 5%, that means that you will earn 5% after one year, not after two.
Same concept when discounting, when you are discounting by the 2-year rate, you are discounting back one year at a time, thus you must raise the discount rate to account for both years.

No I must certainly not in the second case according to Kaplan. It was just in the first case and I didn’t really understand why.

I thought you were talking as a generality. I see what you’re asking now.
The reason you don’t raise in the second example is because you’re not given two-year, three-year, or four-year rates. You are given a whole bunch of one-year rates.

Today, the one-year rate is 5.50%. Next year, the one-year rate will be 7.63%. In two years, the one-year rate will be 12.18%. And in three years, the one-year rate will be 15.50%.

In the first example, you are given n-year rates, which are always quoted in annual terms, thus you must compound them to make the discount match n. In the second example, you are given one-year rates. You don’t need to raise these because they are already annual rates.

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The math works out, if you want to try convert the next year’s one-year rate into today’s two-year rate, two years from now’s one-year rate into today’s three-year rate, and three years from now’s one-year rate into today’s four-year rate. These should all line up to enforce arbitrage.
If you do it that way, then you will need to raise by n.

Ah alright! Gotcha. Thanks for the explanation. Now I understand.

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