Wavelet-based detection of outliers in volatility models

Outliers in financial data can lead to model parameter estimation biases, invalid inferences and poor volatility forecasts. Therefore, their detection and correction should be taken seriously when modeling financial data. This paper focuses on these issues and proposes a general detection and correction method based on wavelets that can be applied to a large class of volatility models. The effectiveness of our proposal is tested by an intensive Monte Carlo study for six well known volatility models and compared to alternative proposals in the literature, before applying it to three daily stock market indexes. The Monte Carlo experiments show that our method is both very effective in detecting isolated outliers and outlier patches and much more reliable than other wavelet-based procedures since it detects a significant smaller number of false outliers

Forecasting stock-return volatility in the time-frequency domain

Este estudo foca nos modelos autorregressivos de heterocedasticidade condicional, em especial nos modelos GARCH. A amostra principal usa dados do retorno do índice do S&P500 ajustados a divisão e dividendos de 1990 a 2008, usando uma janela fora da amostra de 2001 até ao final da amostra. O objetivo principal é analisar o desempenho das previsões do modelo num domínio tempo-frequência e, em seguida, compará-los com resultados em um cenário de domínio de tempo. Para fazer uma análise de domínio tempo-frequência, usamos técnicas de wavelets para decompor as séries temporais S&P500 originais em diferentes frequências, cada uma delas originalmente configurada no domínio do tempo. Em última análise, o objetivo é ver se a decomposição com wavelets traz um desempenho aprimorado na previsão/modelagem da volatilidade, observando a função de perdas de previsão de Quasi-Verossimilhança (QL), bem como os índices médios de perdas de previsão ao quadrado (MSFE). Embora a decomposição com wavelets ajude a capturar componentes periódicos ocultos das séries temporais originais, os resultados de domínio de frequência em termos de função de perda (QL e MSFE) não superam o resultado original do domínio do tempo para qualquer frequência dada. No entanto, a maioria das informações para a volatilidade futura é capturada em poucas frequências da série temporal do S&P500, especialmente, na parte de alta frequência dos espectros, representando horizontes de investimento muito curtos.This research focuses on generalized autoregressive conditional heteroskedasticity (GARCH) model. The main sample uses daily split-adjusted and dividend-adjusted log-return data of the S&P500 index ranging from 1990 to 2008, using an out-of-sample window from 2001 until the end of the sample. The main goal is to analyze the performance of the model forecasts in a time-frequency domain and then to compare them with results in a time-domain scenario. To make a time-frequency domain analysis, this research uses wavelets techniques to decompose the original S&P500 time series into different frequencies brands, each of them originally set in time-domain. Ultimately, the aim is to see if the wavelet decomposition brings an enhanced performance on forecasting/modelling volatility by looking at the Quasi-Likelihood forecasting losses (QL) as well as the mean squared forecasting losses ratios (MSFE). Although the wavelet decomposition helps to capture hidden periodic components of the original time-series, frequency-domain results in terms of loss function (QL e MSFE) don’t outperform the original time-domain result for any given frequency. Nevertheless, most of the information for future volatility is captured in few frequencies of the S&P500 time-series, specially in the high-frequency part of the spectra, representing very short investment horizons

Exchange Volatility and Export Performance in Egypt: New Insights from Wavelet Decomposition and Optimal GARCH Model

This paper assesses the link between exchange volatility and exports in Egypt by combining wavelet analysis with an optimal GARCH model chosen among various extensions. The observed outcomes reveal that this relationship is complex and depends then widely to frequency-to-frequency variation and slightly to leverage effect and to switching regime. Indeed, it is well shown that at the low frequency, the coefficient associated to exchange rate volatility’s effect on trade performance is more intense than that at the high frequency and conversely when subtracting energy share from the total of exports. We attribute the apparently conflicting results to the financial speculation, the composition of trade partners and the choice of reference basket’s currencies

Systemic risk contribution of banks and non-bank financial institutions across frequencies: The Australian experience

The Australian financial sector (AFS) is highly concentrated and interconnected. Besides, Australian banks' lending portfolios are dominated by residential mortgage loans, and 70% of insurance companies' revenues arise from non-policyholder sources. The AFS also performed relatively well during the global financial crisis (GFC). Given these distinctive features, in this paper, we examine the systemic risk contribution of Australian banks, insurance companies, and other financial services providers. We use a flexible copula-based delta conditional value-at-risk (ΔCoVaR) method across different frequencies. Further, we study the systemic risk determinants in a panel setting. We find that the major Australian banks are systemically more important than all other financial institutions. Systemic risk is typically higher after the GFC than in the pre-crisis period, despite the introduction of more stringent capital requirements. In addition, the short-term ΔCoVaR is significantly higher than the medium- and long-term ΔCoVaRs. Finally, institution-specific characteristics and market-wide variables explain the cross-sectional and time-series variation in systemic risk, and their explanatory power varies across frequencies.publishedVersio

Nonlinear Combination of Financial Forecast with Genetic Algorithm

Complexity in the financial markets requires intelligent forecasting models for return volatility. In this paper, historical simulation, GARCH, GARCH with skewed student-t distribution and asymmetric normal mixture GRJ-GARCH models are combined with Extreme Value Theory Hill by using artificial neural networks with genetic algorithm as the combination platform. By employing daily closing values of the Istanbul Stock Exchange from 01/10/1996 to 11/07/2006, Kupiec and Christoffersen tests as the back-testing mechanisms are performed for forecast comparison of the models. Empirical findings show that the fat-tails are more properly captured by the combination of GARCH with skewed student-t distribution and Extreme Value Theory Hill. Modeling return volatility in the emerging markets needs “intelligent” combinations of Value-at-Risk models to capture the extreme movements in the markets rather than individual model forecast.Forecast combination; Artificial neural networks; GARCH models; Extreme value theory; Christoffersen test

Asymmetric effect and dynamic relationships between oil prices shocks and exchange rate volatility: Evidence from some selected MENA countries

The aim of this paper is to investigate the exchange rate consequences of oil-price fluctuations across selected MENA countries (including both commodity importers and exporters) and to examine the dynamic relationship between such shocks. We employed the asymmetry of volatility through the GJR-GARCH model using daily time series data covering the period between 2001 and mi-2015. We refer to impulse responses functions in order to test the dynamic relationships. Empirical results reveal that foreign exchange market and crude oil exhibit asymmetric and no asymmetric in the return series. Additionally, the findings show asymmetric response of volatilities to positive and negative shocks. Furthermore, the results suggest that there is a dynamic relationship among oil price shocks and exchange rate volatility. Indeed, in the short run, oil prices shocks had a significant impact on exchange rate changes. Finally, we found that in the case of oil-exporting country, the oil prices rise may experience exchange rate appreciation, while, the decrease of oil price leads to appreciation of the currency of oil importing countries. This implies that oil prices are a key variable in determining the strength of the currency and its volatility. Therefore, policy makers of most MENA countries should consider exchange rate and oil price fluctuations on their macroeconomic policies and diversify more their economics