Parametric Portfolio Policies: Exploiting Characteristics in the Cross Section of Equity Returns

We propose a novel approach to optimizing portfolios with large numbers of assets. We model directly the portfolio weight in each asset as a function of the asset's characteristics. The coefficients of this function are found by optimizing the investor's average utility of the portfolio's return over the sample period. Our approach is computationally simple, easily modified and extended, produces sensible portfolio weights, and offers robust performance in and out of sample. In contrast, the traditional approach of first modeling the joint distribution of returns and then solving for the corresponding optimal portfolio weights is not only difficult to implement for a large number of assets but also yields notoriously noisy and unstable results. Our approach also provides a new test of the portfolio choice implications of equilibrium asset pricing models. We present an empirical implementation for the universe of all stocks in the CRSP-Compustat dataset, exploiting the size, value, and momentum anomalies.

Cross Market Effects of stocks Short-Selling Restrictions: Evidence from the September 2008 Natural Experiment

Using intraday data, this paper investigates empirically the joint stock and corporate bond markets responses to the September 2008 stocks short sell ban. The study intends to exploit the natural experiment in order to asses the impact of the stock market short sale restrictions (stock market liquidity shock) on corporate bond market variables during the nancial crisis period. The short sell ban was one of the levers that regulators pulled in order to manage the financial crisis. The economic question is whether this lever worked or should have been pulled given the complexity of financial market linkages and news dissemination. Recent financial events suggested that, when market conditions are severe, liquidity can rapidly decline or even disappear. Liquidity shocks are the potential channel through which asset prices are influenced by liquidity. However, the standard theoretical equilibrium asset pricing models do not consider trading and thus ignore the time and cost of transforming cash into financial assets and viceversa hence ignoring the impact of the liquidity shocks. Therefore, investigating liquidity shocks empirically, their transmission across markets is of high interest especially during times of high turbulence as we recently witnessed. We use vector autoregression (VAR) approach to model stock and corporate bond returns, volatilities and transaction costs simultaneously, obtaining an econometric reduced form that incorporates causal and feedback effects among the two markets variables. Using VAR tools, we found that shocks in stock market (short sell ban) had a significant negative impact on corporate bond market variables during the time under investigation.

Short sale constraints, divergence of opinion and asset values: evidence from the laboratory

The overvaluation hypothesis (Miller 1977) predicts that a) stocks are overvalued in the presence of short selling restrictions and that b) the overvaluation increases in the degree of divergence of opinion. We design an experiment that allows us to test these predictions in the laboratory. The results indicate that prices are higher with short selling constraints, but the overvaluation does not increase in the degree of divergence of opinion. We further find that trading volume is lower and bid-ask spreads are higher when short sale restrictions are imposed. JEL Classification: C92, G14 Keywords: Overvaluation Hypothesis , Short Selling Constraints , Divergence of Opinio

High-Speed Natural Selection in Financial Markets with Large State Spaces

Recent research has suggested that natural selection in financial markets may be a very slow process, taking hundreds of years. We show in a general equilibrium model that it may be much faster in markets with large state spaces. In many cases, the time it takes to wipe out irrational investors is inversely proportional to the number of stocks in the market, i.e., if it takes about 500 years with one stock, it takes about one year with 500 stocks. Thus, theoretically, natural selection can be very efficient even when there is high market uncertainty. The speed of the natural selection process is a known function of irrational investors' sentiment and of the real characteristics of the stock market. According to a calibration to U.S. stock data, it takes about fifty years for an irrational investor to be wiped out. This is in line with studies of individual investor underperformance.Asset pricing; Market selection hypothesis; Natural selection

Short sale constraints, divergence of opinion and asset value: Evidence from the laboratory

The overvaluation hypothesis (Miller 1977) predicts that a) stocks are overvalued in the presence of short selling restrictions and that b) the overvaluation increases in the degree of divergence of opinion. We design an experiment that allows us to test these predictions in the laboratory. The results indicate that prices are higher with short selling constraints, but the overvaluation does not increase in the degree of divergence of opinion. We further find that trading volume is lower and bid-ask spreads are higher when short sale restrictions are imposed. --overvaluation hypothesis,short selling constraints,divergence of opinion

The impact of short-selling in financial markets

This dissertation empirically examines the impact of short-selling in financial markets. Given the increasing participation of short-sellers in financial markets, this research provides empirical evidence on an increasingly important issue. Each chapter addresses a research question with scarce or conflicting prior research findings to provide evidence which can assist researchers, investors and regulators to understand and manage the impact of short-selling in financial markets

The impact of short-selling in financial markets

This dissertation empirically examines the impact of short-selling in financial markets. Given the increasing participation of short-sellers in financial markets, this research provides empirical evidence on an increasingly important issue. Each chapter addresses a research question with scarce or conflicting prior research findings to provide evidence which can assist researchers, investors and regulators to understand and manage the impact of short-selling in financial markets

Empirical Limitations on High Frequency Trading Profitability

Addressing the ongoing examination of high-frequency trading practices in financial markets, we report the results of an extensive empirical study estimating the maximum possible profitability of the most aggressive such practices, and arrive at figures that are surprisingly modest. By "aggressive" we mean any trading strategy exclusively employing market orders and relatively short holding periods. Our findings highlight the tension between execution costs and trading horizon confronted by high-frequency traders, and provide a controlled and large-scale empirical perspective on the high-frequency debate that has heretofore been absent. Our study employs a number of novel empirical methods, including the simulation of an "omniscient" high-frequency trader who can see the future and act accordingly