International Scholarly Research Network
ISRN Economics
Volume 2012, Article ID 481856, 5 pages
doi:10.5402/2012/481856
Research Article
Futures Hedges under Basis Heteroscedasticity
Subhankar Nayak and Jacques A. Schnabel
School of Business & Economics, Wilfrid Laurier University, Waterloo, ON, Canada N2L 3C5
Correspondence should be addressed to Jacques A. Schnabel, jschnabel@wlu.ca
Received 30 October 2012; Accepted 26 November 2012
Academic Editors: J. H. Haslag, T. Kuosmanen, and J. Zarnikau
Copyright © 2012 S. Nayak and J. A. Schnabel. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
Minimum variance and mean-variance optimizing hedges are developed when basis risk exhibits heteroscedasticity; that is, the
variance of the difference between spot and futures prices is not constant but rises with the level of spot prices. Two different
hedging objectives are modeled and optimized. The resulting optimality conditions are then interpreted both analytically and
intuitively. Simulations are run to determine whether the model proposed here is superior to the traditional model in terms
of minimizing the hedger’s terminal wealth. The resulting hedge ratios are shown to differ from those that are obtained for
the traditional homoscedastic basis case, but consistent with the extant theoretical paradigm, the demand for futures contacts
is dichotomized into pure hedging and pure speculative components. The simulations demonstrate that, under the statistical
assumptions invoked, the proposed model implies uniformly less hedging and a lower variance of terminal wealth compared with
the traditional model.
1. Introduction
In the usual textbook treatment of the hedging decision,
the basis or the difference between spot and futures prices
is assumed to exhibit a constant variance. Examples are
provided by Duffie[1], Hull [2], and Stulz [3]. The empirical
research that has questioned the validity of this assump-
tion of basis homoscedasticity has sought remediation by
invoking sophisticated econometric techniques that do not
entail the unchanging variance requirement, for example, the
autoregressive conditional heteroscedastic (ARCH) model
invoked by Park and Bera [4] and the generalized autoregres-
sive conditional heteroscedastic (GARCH) model proposed
by Kalimipalli and Susmel [5].
This paper takes a different tack to the issue by examining
how the hedging decision itself changes as a result of remov-
ing the restriction that the basis exhibits a fixed variance.
Formulas for the minimum variance and the mean-variance
optimizing hedges are developed when the variance of the
basis is assumed to increase with the level of spot prices.
2. Basis Heteroscedasticity
This paper examines hedging in the traditional context of a
single-period decision model where the hedge is formed at
time 0, and the hedge is terminated or lifted at time 1. To
provide a concrete decision context, the specific case of a firm
wishing to hedge a foreign currency receivable amounting to
Q that is projected to be received at time 1 is considered. The
foregoing is consistent with the empirical evidence provided
by Grabbe [6], who argues that the basis for foreign currency
contracts exhibits this type of heteroscedasticity.
Define S
0
and S
1
as the spot rates or the values of the for-
eign currency that prevail as the start and end, respectively,
of the period. Employing direct quotation, all exchange rates
considered in this paper are given as the number of domestic
currency units per unit of the foreign currency examined.
Similarly, define F
0
and F
1
as the futures rates that prevail
at the start and end, respectively, of the period. Note that,
whereas S
0
and F
0
are observed at the time the hedge is
formed, S
1
and F
1
are unknown and thus are the random
variables in this discussion. The existing literature on hedg-
ing conventionally assumes that the basis or (S
1
−F
1
) exhibits
an unchanging variance; that is, σ
2
(S
1
− F
1
) is a constant.
Instead of the foregoing, this paper conjectures the
percentage basis or the basis calculated as a percent of the
spot rate; that is, e = (S
1
−F
1
)/S
1
exhibits a constant variance.
Stated another way, this paper assumes that the basis itself,
(S
1
− F
1
), exhibits a variance that rises with S
1
. Thus, a