# Essays on Banking and Portfolio Choice

Abstract: This thesis consists of three self-contained essays in the fields of banking and portfolio choice.Banking and Optimal Reserves in an Equilibrium Model:I address the question of reserves in banking, particularly the fact that reserves are substantially larger than the stipulated reserve requirements by Bank of International Settlements. My contribution is to show that when the underlying values of borrowers are correlated, banks should hold positive reserves, regardless of the regulation. I use a derived distribution for debt portfolios to show that intermediation in a debt market will outperform direct lending, even if intermediaries are allowed to default. The model used is a generalization of Williamson (1986), with Costly State Verification as asymmetric information. By using a factor model for the value of entrepreneurs' projects, I introduce a positive probability for banks to default. It is shown that, in equilibrium, banks choose to hold capital reserves that are almost large enough to eliminate the expected auditing cost for their depositors. The reason is that auditing does not provide any utility and hence, the cake to be split between banks and depositors is enlarged by reserves as an insurance against bad outcomes. It is also shown that the more correlation there is in the debt portfolio, the larger is the optimal reserve level. This could explain why small regional banks in Sweden often have more than twice the reserve level of their nation-wide competitors.Optimal Rebalancing of Portfolio Weights under Time-varying Return Volatility:This paper considers horizon effects on portfolio weights under time varying and forecastable return volatility. The return volatility is modeled as a GARCH-M, which is sufficiently general to encompass both constant and time varying means. The analysis confirms earlier results, namely that there are no horizon effects when the stochastic process, which governs asset returns, has a constant mean. However, when time varying and forecastable volatility is included in the mean equation, there are horizon effects. I show three features to be of importance for the horizon effect: First, the size of the parameter on conditional volatility in the mean equation and second, persistence in conditional volatility. Third, the asymmetry in volatility has some effect. In addition, the parameter of relative risk aversion is important. For low levels of risk aversion, only very small effects on portfolio weights are present; when the level of risk aversion increases, so does the effects on portfolio weights. Portfolio weights increase for the first 2-3 years when the investment horizon is increased; the total effect slightly exceeds 10%.Can Parameter Uncertainty Help Solve the Home Bias Puzzle?A well-known puzzle in international finance is the equity home bias. This paper illustrates a mechanism where exchange rate estimation risk causes equity home bias. Estimation risk is introduced into a standard mean-variance portfolio framework by having return time series with different lengths. We argue that the exchange rate return history, which is a part of the local currency return on a foreign investment, is likely to be substantially shorter than the available return histories of equity indices due to, for example, exchange rate regime shifts. To econometrically deal with return histories of different lengths we utilize a framework devised by Stambaugh (1997). The impact of estimation risk on an optimal portfolio is tested with data from Sweden and the U.S. Our results suggest that explicitly accounting for estimation risk causes the domestic investor to increase his fraction of domestic assets. While the introduction of exchange rate estimation risk is not powerful enough to explain the whole home bias observed in data, the results of this paper illustrate a mechanism that is often overlooked in discussions of international portfolio diversification.

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