Seasonal adjustment and cointegration

We examine the effects of seasonal adjustment filters on the size and power of ADF and PP residual-based cointegration tests via a Monte Carlo and an empirical application. Our results indicate that the use of filters distorts the size and reduces the power of these tests.Seasonal adjustment, linear filters, cointegration

Testing for seasonal unit roots in heterogeneous panels

This paper uses the approach of Im, Pesaran and Shin (2003) to propose seasonal unit root tests for dynamic heterogeneous panels based on the means of the individuals HEGY test statistics. The standardised t-bar and F-bar statistics are simply averages of the HEGY tests across groups. These statistics converge to standard normal variateHeterogeneous dynamic panels, Monte Carlo, seasonal unit roots

The KPSS Test with Outliers

We investigate the effects of outliers on the KPSS tests. We find that for nonstationary series outliers induce spurious stationarity by lowering the power of these tests. The empirical size of these tests is also found to be sensitive to the location of the outlier.KPSS test ; Monte Carlo ; outliers ; power ; size

Modelling official and parallel exchange rates in Colombia under alternative regimes: a non-linear approach (Corrected version)

We examine the long-run relationship between the parallel and the official exchange rate in Colombia over two regimes; a crawling peg period and a more flexible crawling band one. The short-run adjustment process of the parallel rate is examined both in a linear and a non-linear context. We find that the change from the crawling peg to the crawling band regime did not affect the long-run relationship between the official and parallel exchange rates, but altered the short-run dynamics. Non-linear adjustment seems appropriate for the first period, mainly due to strict foreign controls that cause distortions in the transition back to equilibrium once disequilibrium occurs. ********************************************************************** En este documento se analiza la relación a largo plazo entre la tasa de cambio oficial y paralela de Colombia, bajo dos régimenes distintos, un periódo de crawling-peg y un periódo más flexible de banda cambiaria. Se analiza el proceo de ajuste a corto plazo de la tasa paralela bajo contextos lineal y no lineal. Como conclusión se detectó que el cambio de régimen de tasa de cambio no afectó la relación a largo plazo entre la tasa de cambio oficial y la paralela, pero sí modificó la relación a corto plazo. Un método de ajuste no lineal parece ser apropiado para formalizar el comportamiento en el primer periodo, principalmente debido a los estrictos controles externos que generan distorsiones en el proceso de retorno al equilibrio, cuando un desequilibrio ha ocurrido.Parallel market, cointegration, non-linear error correction models, Colombia

Pricing behaviour under competition in the UK electricity supply industry

This paper investigates the evolution of electricity prices for domestic customers in the UK following the introduction of competition. The empirical analysis is based on a panel data set containing detailed information about electricity supply prices over the period 1999 to 2006. The analysis aims to test theoretical hypotheses about the nature of consumers’ switching and search costs. The econometric analysis of persistence and price dispersion provides only limited support for the view that the market is becoming more competitive and also indicates that there remain significant potential benefits to consumers from searching alternative suppliers

An estimation of the pattern of diffusion of mobile phones: the case of Colombia

In this paper we fond that the difusion pattern of mobile telephony in Colombia can be best haracterised as following a Logistic curve. Although in recent years the rate of growth of mobile phone subscribers has started to slow down, we find evidence that there is still room for further expansion as thesaturation level is expected to be reached in five years time. The estimated saturation level is consistent with some individuals possessing more than one mobile device.Technology di¤usion; Mobile telecommunications; Gompertzcurve; Logistic curve; Colombia.

Testing for Seasonal Unit Roots in Heterogeneous Panels

This paper uses the approach of Im, Pesaran and Shin (2003) to propose seasonal unit root tests for dynamic heterogeneous panels based on the means of the individuals HEGY test statistics. The standardised t-bar and F-bar statistics are simply averages of the HEGY tests across groups. These statistics converge to standard normal variates.Heterogeneous dynamic panels ; Monte Carlo ; seasonal unit roots

Forecasting the spot prices of various coffee types using linear and non-linear error correction models

This paper estimates linear and non-linear error correction models for the spot prices of four different coffee types. In line with economic priors, we find some evidence that when prices are too high, they move back to equilibrium more slowly than when they are too low. This may reflect the fact that, in the short run, it is easier for countries to restrict the supply of coffee in order to raise prices, rather than increase supply in order to reduce them. Further, there is some evidence that adjustment is faster when deviations from the equilibrium level get larger. Our forecasting analysis suggests that asymmetric and non-linear error correction models offer weak evidence of improved forecasting performance relative to the random walk model. *********************************************************************** Este documento estima modelos lineales y no-lineales de corrección de errores para los precios spot de cuatro tipos de café. En concordancia con las leyes económicas, se encuentra evidencia que cuando los precios están por encima de su nivel de equilibrio, retornan a éste mas lentamente que cuando están por debajo. Esto puede reflejar el hecho que, en el corto plazo, para los países productores de café es mas fácil restringir la oferta para incrementar precios, que incrementarla para reducirlos. Además, se encuentra evidencia que el ajuste es más rápido cuando las desviaciones del equilibrio son mayores. Los pronósticos que se obtienen a partir de los modelos de corrección de errores no lineales y asimétricos considerados en el trabajo, ofrecen una leve mejoría cuando se comparan con los pronósticos que resultan de un modelo de paseo aleatorio.Coffee prices, asymmetric and non-linear error correction models, forecasting

Testing for stationarity in heterogeneous panel data in the presence of cross section dependence

The panel variant of the KPSS tests developed by Hadri (2000) for the null of stationarity suffers from size distortions in the presence of cross section dependence. However, applying the bootstrap methodology we find that these tests are approximately correctly sized.Heterogeneous dynamic panels ; Monte Carlo ; bootstrap ; unit root tests ; cross section dependence.

Testing for seasonal unit roots in heterogeneous panels in the presence of cross section dependence

This paper presents two alternative methods for modifying the HEGY-IPS test in the presence of cross-sectional dependency. In general, the bootstrap method (BHEGY-IPS) has greater power than the method suggested by Pesaran (2007) (CHEGY-IPS), although for large T and high degree of cross-sectional dependency the CHEGY-IPS test dominates the BHEGY-IPS test.Heterogeneous dynamic panels ; Monte Carlo ; seasonal unit roots ; cross sectional dependence