hull chapter 7 swaps questions clarification

puneet_

Member
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hi, can you some please help me here? why did we convert forward rates from cc to semi annual? it could be very basic/stupid question. to me cc is something keeps on compounding every second as interest accrues, it starts to compound so why 10.75 turned to 11.04? thanks

Screen Shot 2016-03-22 at 12.23.30 pm.png
 

ami44

Well-Known Member
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The forward rates are converted into semi-annual compounded rates, so that the interest amount can be calculated by the simple formula
CF = ForwardRate * Notional * DeltaT

Please note, that semi-annual compounding is chosen, because than the pay-frequency and compounding frequency are identical, this is also called simple interest rate.

Of course strictly speaking the conversion is not necessary, since the interest can be calculated directly from the cont. compounded rate by:
CF = Notional * ( exp(ForwardRate * DeltaT) - 1 )

But the Author decided to do this calculation in two steps instead, I guess for reasons of clarity.

Did that answer your question?
 

ami44

Well-Known Member
Subscriber
Additionally to my remarks above, I think I found an error in the example.
If you look at the forward rates, than you see that they are calculated from the Libor rates with the formula for continuous compounding e.g.:
10.75 = (0.75 * 10.5 - 0.25 * 10) / 0.5

But the libor rates are not continuous compounded, they are given as simple interest. So the libor rates and forward rates shown are not compatible.

I see no reason to use continuous compounding at all in the calculation, but of course I judge solely from the screenshot. The rest of the video might offer explanation for that.
 

David Harper CFA FRM

David Harper CFA FRM
Subscriber
@ami44 your first explanation is exactly correct. This is from Hull: his assumptions include LIBOR rates with continuous compounding (it's always the case with Hull that spot/zero rates are given with continuous compounding), but the swap's pay fixed rate is given with semi-annual compounding (i.e., to match the payment frequency). So, the assumptions do not match, as given, such that the conversion is necessary. Thanks!
 

ami44

Well-Known Member
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OK, I will not say anything about compounding again. That is the second time now that I'm surprised by continuous compounding.

Of course actual Libor rates are not continuously compounded, but I guess Hull is using it out of educational reasons.
 
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