Robust portfolio choice with stochastic interest rates

We determine the optimal investment strategy for an ambiguity-averse investor in a setting with stochastic interest rates. The investor has access to stocks, bonds, and a bank account and he is ambiguous about the expected rate of return of both bonds and stocks. The investor can have different levels of ambiguity aversion about the two types of risky assets. We find that it is more important to take model uncertainty about the stock dynamics than model uncertainty about the bond dynamics into account. Furthermore, the investor’s ambiguity increases his hedging demand. Consequently, the bond/stock ratio increases with his ambiguity and implies less extreme positions in the bank account. Altogether, our model yields portfolio allocations which are more in line with what is implementable in practice. Finally, we demonstrate that neglecting model uncertainty implies significant losses for the investor.     

Optimal mean-reversion strategy in the presence of bid-ask spread and delays in capital allocations

A portfolio optimization problem for an investor who trades T-bills and a mean-reverting stock in the presence of proportional and convex transaction costs is considered. The proportional transaction cost represents a bid-ask spread, while the convex transaction cost is used to model delays in capital allocations. I utilize the historical bid-ask spread in US stock market and assume that the stock reverts on yearly basis, while an investor follows monthly changes in the stock price. It is found that proportional transaction cost has a relatively weak effect on the expected return and the Sharpe ratio of the investor's portfolio. Meantime, the presence of delays in capital allocations has a dramatic impact on the expected return and the Sharpe ratio of the investor's portfolio. I also find the robust optimal strategy in the presence of model uncertainty and show that the latter increases the effective risk aversion of the investor and makes her view the stock as more risky.     

Interest Rate Risk Rewards in Stock Returns of Financial Corporations: Evidence from Germany

The interest rate sensitivity of stock returns of financial and non-financial corporations is a well-known phenomenon. However, only little is known about the part of total stock returns that is attributable to the compensation an investor receives for being exposed to interest rate risk when investing in equity securities. We pursue here a benchmark portfolio approach, constructing benchmark portfolios having the same interest rate risk exposure as a particular stock. By studying the time series of returns of these asset-specific benchmarks, we find: i) Regardless of the industry considered, the interest rate risk benchmarks of German corporations have mostly earned a significantly positive reward. ii) Returns of interest rate risk benchmarks of financial institutions exceeded significantly those of non-financial corporations. iii) An investor willing to bear nothing but the average interest rate risk of German financial institutions would have earned a mean return of about or even exceeding 70% of the corresponding total stock returns. iv) Returns of the interest rate risk benchmarks of the German insurance sector were significantly higher than those of German banks, which seems to contradict conventional market wisdom that insurances hedge interest rate risks.     

Agency Conflicts, Investment, and Asset Pricing

The separation of ownership and control allows controlling shareholders to pursue private benefits. We develop an analytically tractable dynamic stochastic general equilibrium model to study asset pricing and welfare implications of imperfect investor protection. Consistent with empirical evidence, the model predicts that countries with weaker investor protection have more incentives to overinvest, lower Tobin's q, higher return volatility, larger risk premia, and higher interest rate. Calibrating the model to the Korean economy reveals that perfecting investor protection increases the stock market's value by 22%, a gain for which outside shareholders are willing to pay 11% of their capital stock.     

A dynamic equilibrium model for U-shaped pricing kernels

This paper proposes a dynamic equilibrium model that can provide a unified explanation for the stylized facts observed in stock index markets such as the fat tails of the risk-neutral return distribution relative to the physical distribution, negative expected returns on deep OTM call options and negative realized variance risk premiums. In particular, we focus on the U-shaped pricing kernel against the stock index return, which is closely related to the negative call returns. We assume that the stock index return follows a time-changed Lévy process and that a representative investor has power utility over the aggregate consumption that forms a linear regression of the stock index return and its stochastic activity rate. This model offers a macroeconomic interpretation of the stylized facts from the perspective of the sensitivity of the activity rate and stock index return on aggregate consumption as well as the investor’s risk aversion.     

Portfolio management with stochastic interest rates and inflation ambiguity

We solve, in closed form, a stock-bond-cash portfolio problem of a risk- and ambiguity-averse investor when interest rates and the inflation rate are stochastic. The expected inflation rate is unobservable, but the investor can learn about it from observing realized inflation and stock and bond prices. The investor is ambiguous about the inflation model and prefers a portfolio strategy which is robust to model misspecification. Ambiguity about the inflation dynamics is shown to affect the optimal portfolio fundamentally different than ambiguity about the price dynamics of traded assets, for example the optimal portfolio weights can be increasing in the degree of ambiguity aversion. In a numerical example, the optimal portfolio is significantly affected by the learning about expected inflation and somewhat affected by ambiguity aversion. The welfare loss from ignoring learning or ambiguity can be considerable.     

REIT Risk Premium Sensitivity and Interest Rates

This analysis investigates several aspects of the relationship between daily REIT stock risk premiums and various interest rates. Consistent with prior research, the general findings indicate that interest rates do impact REIT returns. This study specifically finds that stock returns are more sensitive to maturity rate spread between short- and long-term treasuries than the credit rate spread between commercial bonds and treasuries. In addition, the analyses document a structural model shift during the nineties that has made REITs more sensitive to credit risk. In additional to change in investor clientele, an analysis of declining REIT credit-worthiness points to a root cause for this shift.     

Capital income taxation and risk taking under prospect theory

This research examines capital income taxation for a prospect theory investor under some acceptable in the literature reference levels relative to which are the changes in the level of wealth valued. Depending on the reference level, some results indicate that it is possible for a capital income tax increase not to stimulate risk taking even if the tax code provides attractive full loss offset provisions. However, risk taking can be stimulated when investors compare their reference level with others. Risk taking can increase also if the investor interprets part of the tax as a loss instead as a reduced gain. Then the investor becomes risk seeking and moves away from the discomfort zone of relative losses. This later response to taxation causes private risk taking to increase.     

General equilibrium real and nominal interest rates

We derive the general equilibrium short-term real and nominal interest rates in a monetary economy affected by technological and monetary shocks and where the price level dynamics is endogenous. Assuming fairly general processes for technology and money supply, we show that an inherent feature of our equilibrium is that any real variable dynamics, in particular that of the short-term real interest rate, is driven by both monetary and real factors. This money non-neutrality is generic, as it does not stem from any friction such as price stickiness, or from a particular utility function. Non-neutrality obtains because the ex ante cost of real money holdings is random due to inflation uncertainty. We then analyze in depth a specialized version of this economy in which the state variables follow square root processes, and the representative investor has a log separable utility function. The short-term nominal rate dynamics we obtain encompasses most of the dynamics present in the literature, from Vasicek and CIR to recent quadratic and, more generally, non-linear interest rate models. Moreover, our results pave the way to several new nominal term structures.     

A股税收客户群效应及除息日税负效应实证研究

本文分析了2002—2007年A股市场的纯现金红利分红数据,检验了这一期间在除息日套利的可能性,证实该期间市场存在除息日股价的税负效应,以及税收客户群效应。说明A股市场不同类的投资者对分红具有不同的偏好,上市公司应制定合适的股利政策以最大化股东财富。早期的关于国内市场的研究得到市场不存在税收客户群效应的结论,前后对比说明随着国内证券市场的发展,投资者更趋于理性。