
Chapter 20: Interest rate risk
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In this way, prices for STIRs move in the same way as cash market prices for bonds
and other interest products.
4.7 Hedging short-term interest rate exposures with STIRs
STIRs can be used to hedge exposures to the risk of a rise or fall in short-term
interest rates between the time the future is sold or bought and the settlement date
for the future. Most STIRs are traded for settlement dates within the next six months
or so. Using short-term interest rate futures is similar to using currency futures to
hedge a currency exposure. However, the following rules need to be applied:
If the aim is to hedge against the risk of an increase in the short-term interest
rate, the hedge is created by
selling futures. If the interest rate does go up,
futures prices will fall, and there will be a profit on the short position in STIRs
If the aim is to hedge the risk of a fall in the short-term interest rate, the hedge is
created by
buying futures.
Example
It is February. A company intends to borrow £10 million in June for three months
and for simplicity it is assumed that the company can borrow at the LIBOR rate. It
decides to hedge its exposure to a rise in the LIBOR rate between ‘now’ and June by
selling June sterling interest rate futures. Suppose the selling price for the futures is
94.00 (= 6%).
When the futures reach their settlement date in June, the actual LIBOR rate might be
7.5%. If so, the company will borrow £10 million at 7.5%. However, in settlement of
its futures position, it has sold notional deposits at 6% and on settlement buys them
back at the current LIBOR rate of 7.5%, giving itself a 1.5% profit on the futures
trading. Its net effective interest cost for the next three months is therefore 7.5% -
1.5% = 6%, which is the rate at which it sold the futures in February.
If the LIBOR rate at settlement in June had been 5.5%, the company would have
borrowed for thee months at 5.5% but would have made a loss on settlement of its
futures position. The loss would be 0.5% (= 6% - 5.5%) and so its effective interest
cost for the next three months would be 5.5% + 0.5% loss = 6% - the rate fixed by the
sale of the futures in February.
Number of futures for a hedge
If a company knows that it will need to borrow $20 million for three months in
September, and that the borrowing rate will be linked to dollar LIBOR, it can sell
September futures. Since each future is for a three-month deposit of $20 million, it
will need to sell 20 September futures.
Short-term interest rate futures are futures for three-month deposits. If a company
wishes to hedge an interest rate risk for a different interest period, such as two
months, four months or six months, the number of futures to create the hedge
should be adjusted by a factor:
(Interest period to be hedged/3 months).