- Augustine C. Arize
- Charles J. Berendt
- Giuliana Campanelli Andreopoulos
- Ioannis N. Kallianiotis
- John Malindretos
This paper uses a large variety of different models and examines the predictive performance of these exchange rate models by applying parametric and nonparametric techniques. For forecasting, we will choose that predictor with the smallest root mean square forecast error (RMSE). The results show that better models are equations (54), (46), (34), (39) and (53), but none of them gives a perfect forecast. At the end, error correction versions of the models will be fit so that plausible long-run elasticities can be imposed on the fundamental variables of each model.
Many economic time series do not have a constant mean and most exhibit phases of relative tranquility followed by periods of high volatility. Casual inspection of exchange rates and many other economic time series data suggest that they do not have a constant mean and variance. (A stochastic variable with a constant variance is called homoscedastic, as opposed to heteroscedastic.) For series exhibiting volatility, the
unconditional variance may be constant even though the variance during some periods is unusually large. The trends displayed by some variables may contain deterministic or stochastic components. In our analysis, it actually makes a great deal of difference if a series is estimated and forecasted under the hypothesis of a deterministic versus a stochastic trend.
By graphing the different exchange rates, we can illustrate their behavior just by looking at the fluctuation of these rates over time. Of course, formal testing is necessary to substantiate any first impressions. The first visual pattern is that these series are not stationary, in that the sample means do not appear to be constant and there is a strong appearance of heteroscedasticity. It is hard to maintain that these series do have a time-invariant mean. They do not contain a clear trend. The dollar/pound exchange rate shows no particular tendency to increase or decrease. The dollar seems to go through sustained periods of appreciation and then depreciation without a tendency of reverting to a long-run mean.
This type of “random walk” behavior is typical of nonstationary series. Any shock to the series displays a high degree of persistence. Notice that the $/£ exchange rate experienced a violently upward surge in 1980 and remained at this higher growth for nearly four years; it
returned to almost its previous level after nine years.
The volatility of these series is not constant over time. (Such series are called conditionally heteroscedastic if the unconditional or long-run variance is constant but there are periods in which the variance is relatively high.) Some exchange rates series share comovements
with other series. Large shocks to the U.S. appear to be timed similarly to those in the U.K. and Canada. The presence of such co-movements should not be too surprising. We might expect that the underlying economic forces affecting the U.S. economy also affect the economy internationally.