Aslihan Altay-Salih

Time-Varying Betas Help in Asset Pricing: The Threshold CAPM

Although there is a consensus about time variation in market betas, it is not clear how this variation should be captured. Several researchers continue to analyze different versions of the conditional CAPM. However, Ghysels (1998) shows that these conditional CAPM models fail to capture the dynamics of beta risk. In this study, we introduce a new model, threshold CAPM, which outperforms both the conditional and unconditional CAPMs by generating smaller pricing errors. We also show that the beta risk changes through time with the changes in the economic environment and the dynamics of time variation of beta differ across industries. These findings have important implications for asset allocation, portfolio selection, and hedging decisions.

Exploring exchange rate returns at different time horizons

This paper explores and compares the empirical distribution of the US dollar–deutsche mark exchange rate returns with well-known continuous-times processes at different frequencies. We use a variety of parametric models to simulate the unconditional density of the exchange rate returns at different frequencies, and show that the studied models do not fit the empirical distribution of exchange rate returns at both the high and low frequencies.

Constrained Nonlinear Programming for Volatility Estimation with GARCH Models

This paper proposes a constrained nonlinear programming view of generalized autoregressive conditional heteroskedasticity (GARCH) volatility estimation models in financial econometrics. These models are usually presented to the reader as unconstrained optimization models with recursive terms in the literature, whereas they actually fall into the domain of nonconvex nonlinear programming. Our results demonstrate that constrained nonlinear programming is a worthwhile exercise for GARCH models, especially for the bivariate and trivariate cases, as they offer a significant improvement in the quality of the solution of the optimization problem over the diagonal VECH and the BEKK representations of the multivariate GARCH model.

Foreign Equity Trading and Average Stock-return Volatility: FOREIGN EQUITY TRADING AND VOLATILITY

We examine whether there is a relationship between foreign equity trading and average total volatility, measured as the value-weighted average of stock-return variance in the Istanbul Stock Exchange. We employ foreign equity purchase and sale data to track changes in foreign equity trading, which not only enable us to capture effective foreign investor participation but also to observe the potential asymmetric effects of incoming and outgoing funds on the average total volatility. Consistent with the implications of the asymmetric information hypothesis, we find that net equity flow is positively associated with average total volatility. Furthermore, we show that net equity flow affects the average total volatility through the local and idiosyncratic volatilities, suggesting that foreign investors engage in the production of firm specific and market wide information.

Performance of the efficient frontier in an emerging market setting

This study applies the Markowitz analysis to the Istanbul Stock Exchange and empirically investigates the performance of this tool in an emerging market setting. The results show that during the early years of establishment of an emerging stock exchange, an active strategy of mean variance portfolio, investing with monthly balancing, outperforms the passive strategies. However, at later stages the capital market liberalization changes market participants. Together, with the increase in foreign participation and integration of the market with the rest of the world, the performance of means variance efficient portfolios detoriate. The study also reports that the strategy is not effective during financial crisis.

Do Time-Varying Betas Help in Asset Pricing? Evidence from Borsa Istanbul

ABSTRACT We investigate the time variation in the market risk of industry portfolios of Borsa Istanbul with respect to changes in economic conditions by employing the threshold CAPM. The threshold CAPM defines beta as a function of an underlying economic variable, the threshold variable, to allow beta to change between two different regimes when the threshold variable hits a certain threshold level. We use interest rate, currency basket, real effective currency index, and market volatility as candidates for the threshold variable. We find there is a significant time variation in betas with respect to changes in the currency basket level.

Aggregate Volatility Expectations and Threshold CAPM

We propose a volatility-based capital asset pricing model (V-CAPM) in which asset betas change discretely with respect to changes in investors’ expectations regarding near-term aggregate volatility. Using a novel measure to proxy uncertainty about expected changes in aggregate volatility, i.e. monthly range of the VIX index (RVIX), we find that portfolio betas change significantly when uncertainty about aggregate volatility expectations is beyond a certain threshold level. Due to changes in their market betas, small and value stocks are perceived as riskier than their big and growth counterparts in bad times, when uncertainty about aggregate volatility expectations is high. The proposed model yields a positive and significant market risk premium during periods when investors do not expect significant uncertainty in near-term aggregate volatility. Our findings support a volatility-based time-varying risk explanation.

On the performance of West's bubble test: A simulation approach

Abstract In this research we examine the ability of West’s bubble test [1] in detecting speculative bubbles using Brock’s (1982) [2] intertemporal general equilibrium model of asset pricing as the basis for a simulation study. In this setting, (1) the economy, by construction is efficient and produces the maximally possible amount of welfare for society, and (2) asset prices reflect the utility-maximizing behavior of consumers and the profit-maximizing behavior of firms. We find that the West’s bubble test flag as “bubbles” in the simulated data yet the data is produced from an economy in which markets are efficient in welfare production.