Long-run equity risk and dynamic trading strategies: a simulation exercise for the Italian stock market

Abstract

The paper develops a simulation approach capable of reproducing the high frequency characteristics of Italian stock market prices, without assuming any specific form for their stochastic process. The approach is then used to verify the capability of dynamic trading strategies to protect against downside risk in the long run. Because a fully funded capitalized retirement system will develop in Italy in the near future, dynamic trading strategies might become a widely used tool among Italian portfolio managers to hedge long-run equity risk, especially in view of the poor risk –return trade off that the stock market has historically provided. Both option replicating strategies and constant proportion strategies are simulated. The impact of transaction costs, non stationary return variances, alternative portfolio rebalancing schemes and various implementation constraints on the strategies cost are examined. For the option replicating strategies, ex posteffective costs turn out to be close to ex antetheoretical expected cost. The crucial element in the strategy appears the decisions about the length of the option strategy and the rule to reset the floor at the end of it. Constant proportion strategies are cheaper and easier to implement, but their effectiveness depends too on the way in which the floor is adjusted as a function of the stock price movements. Broadly speaking, the simulations confirm that dynamic strategies are capable of delivering what they are supposed to achieve. All types of strategies are relatively straightforward and can be used with an acceptable margin of uncertainty.