Working out conversion factors for Treasury Bond Futures.

Hi all,

There's something that I just can't make sense of and would appreciate some help.

When calulating the conversion factor for a Treasury Bond Future, we round down the maturty date to the nearest 3 months period. So we can have the situation where there is an extra 3 months when we semi annualize the bonds present value.

Now the example in Hull is confusing me. I've attached a spreadsheet that shows the present value of the bond. This is in cells M26:P61 on sheet1. I've scanned in the formula that hull uses from his book and placed it on the sheet. Both prices are the values of $125.83

However, the things I don't understand are:
1. The pricing of the bond, according to the Hull text, is to 3 months time. I believe that the bond is actually calculated to discount to the present time not 3 months!

For example the 1st coupon payment is worked out to be discounted to a factor 0.9708 for a 0.5 period to the present day.

4, 0.5, 0.970873786, 3.883495146

How can Hull work this out to be 3 months??
Surely the 1st time period used for calculating the price would be 0.25 - i.e. 3 months (0.25). This would yield a different price.

2. If you look at the formula scanned in the spreadsheet, he deals with the extra 3 months coupon by simply adding the a coupon payment of 4. How on earth does that add up? Wouldn't the extra 3 months 'at the maturity' of the bond need to be discounted back to a price today?? How can you just add an additional coupon payment not pv'ed or anything.

I can't make head or tails of this.
Any help is really appreciated

Thanks in advance,
Paul
 
Hi,

Thanks for your reply but I got an answer from www.bionicturtle.com - it's a quality site!

Basically, Hull is examining the cash flows from the 1st coupon payment and so the $4 is that coupon payment.

If you do the ALL cash flows again and include the $4 coupon i.e. 37 in total then pv the bond, and then compound it forward 3 months you'll get the price that Hull does. Hull works it out to the 3 months then discounts it back. Effectively the same just one easier to understand :)

Thanks,
Paul
 
Quote from Paul_G:
.....just one easier to understand :)
As long as you're able to somehow, someway, make money trading bonds with that info, then it's okay. :)
 
Hi,

I'm just working through Hull to understand how these things are priced etc. I'm not going to trade these instruments, although I'm a believer in knowing the details of how things are calculated.

Thanks
Paul
 
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