K. Zhang et al.
10.4236/tel.2018.81001 2 Theoretical Economics Letters
different financial instruments and markets around the world. Important
financial decisions such as portfolio optimisation, derivative pricing, risk
management and financial regulation heavily depend on volatility forecasts. In
derivative pricing, such as in the estimation of the Black-Scholes option pricing
model, volatility is the only parameter that needs to be forecasted. The
prediction of volatility is also crucial in development of Value at Risk (VaR) and
a variety of systemic risk models, as well as in banking and finance regulations.
For example, according to the Basel Accord II and III, it is compulsory for all
financial institutions to predict the volatility of their financial assets to
incorporate the risk exposure of their capital requirements.
The focus of our study is on the predictive ability of the popular
AutoRegressive Conditional Heteroscedastic (ARCH) class of models that
originated from a seminal Nobel Prize-wining article by [1] [2] generalized his
framework to obtain the GARCH model. ARCH and GARCH models are
popular and standard volatility forecasting models in econometrics and finance.
Documented stylized features of variation such as the clustering and long
memory effect can be captured by GARCH class models, and the model
parameters are relatively easy to estimate. A comprehensive survey of the
GARCH family of models can be found in [3]. The current study selects three
popular GARCH class models from the literature, including the standard
GARCH, the threshold GARCH (TGARCH) of [4] and [5], and the asymmetric
power ARCH (APARCH) of [6]. In addition to the three standard models, we
consider 12 corresponding forecasting strategies associated with them, which
involves different estimation windows and errors distributions.
The predictive power of a volatility model is evaluated based on an
out-of-sample test in which the predicted volatility generated from the model is
compared with the
ex
-
post
volatility measurements. Superior volatility forecasting
models are supposed to have small forecasting errors, measured as the difference
between the predicted and actual volatility. However, unlike the return, the
volatility process cannot be observed. Therefore, in out-of-sample evaluation of
volatility forecasting models, the crucial task is to find an accurate proxy for the
underlying unobserved volatility process. In the mid-1990s, a series of empirical
studies noted that while GARCH-type models are for fitting the time series
returns, they failed to explain much of the variability in
ex
-
post
volatility
measured by the squared returns in out-of-sample tests. Hence, the practical
usefulness of GARCH models was challenged. [7] responds to the critique of the
model and argues that the unsatisfied empirical results are due to the noisy
volatility proxies used in these studies, that is, squared returns or absolute
returns. In out-of-sample forecast evaluation, a common approach for
evaluating the practical performance of any model is to compare the fitted
predictions derived from the model with the subsequent realizations. However,
volatility is not directly observed and dealt with as a latent variable in financial
modelling. Therefore, the squared innovation return is usually employed as a
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