A mean/variance approach to long-term fixed-income portfolio allocation

Abstract

Long-term investments in bonds offer known returns, but with risks corresponding to defaults of the underwriters. The excess return for a risky bond is measured by the spread between the expected yield and the risk-free rate. Similarly, the risk can be expressed in the form of a default spread, measuring the difference between the yield when no default occurs and the expected yield. For zero-coupon bonds and for actual market data, the default spread is proportional to the probability of default per year. The analysis of market data shows that the yield spread scales as the square root of the default spread. This relation expresses the risk premium over the risk-free rate that the bond market offers, similarly to the risk premium for equities. With these measures for risk and return, an optimal bond allocation scheme can be built following a mean/variance utility function. Straightforward computations allow us to obtain the optimal portfolio, depending on a pre-set risk-aversion level. As for equities, the optimal portfolio is a linear combination of one risk-free bond and a risky portfolio. Using the scaling law for the default spread allows us to obtain simple expressions for the value, yield and risk of the optimal portfolio.     

Differential risk premiums and the UIP puzzle

We respecify the uncovered interest rate parity (UIP) conditions by inverting the market price of the risk (Sharpe ratio) formula. Our empirical model provides new insight indicating that violations to the UIP stem from the existence of a risk premium in the exchange rates and from observed market return differentials being a noisy statistic of the markets’ expected return differentials in our respecified model. Using an integrated macro‐micro structure framework for expected market return differentials improves our model fit and the validity of UIP.     

On the Lack of Participating Policy Usage by Stock Insurance Companies

Stock insurers can reduce or eliminate agency conflicts between policyholders and stockholders by issuing participating insurance. Despite this benefit, most stock companies don't offer participating contracts. This study explains why. We study an equilibrium with both stock and mutual insurers in which stockholders set premiums to provide a fair expected return on their investment, and with a policyholder who chooses the insurance contract that maximizes her expected utility. We demonstrate that stockholders cannot profitably offer fully participating contracts, but can profitably offer partially participating insurance. However, when the policyholder participation fraction is high, the fair‐return premium is so large that the policyholder always prefers fully participating insurance from the mutual company. Policies with lower levels of policyholder participation are optimal for policyholders with relatively high risk aversion, though such policies are usually prohibited by insurance legislation. Thus, the reason stock insurers rarely issue participating contracts isn't because the potential benefits are small or unimportant. Rather, profitability or regulatory constraints simply prevent stock insurers from exercising those benefits in equilibrium.     

A Required Yield Theory of Stock Market Valuation and Treasury Yield Determination

Stock market valuation and Treasury yield determination are consistent with the Fisher effect (1896) as generalized by Darby (1975) and Feldstein (1976) . The U.S. stock market (S&P 500) is priced to yield ex-ante a real after-tax return directly related to real long-term GDP/capita growth (the required yield ). Elements of our theory show that: (1) real after-tax Treasury and S&P 500 forward earnings yields are stationary processes around positive means; (2) the stock market is indeed priced as the present value of expected dividends with the proviso that investors are expecting fast mean reversion of the S&P 500 nominal growth opportunities to zero. Moreover, (3) the equity premium is mostly due to business cycle risk and is a direct function of below trend expected productivity, where productivity is measured by the growth in book value of S&P 500 equity per-share. Inflation and fear-based risk premia only have a secondary impact on the premium. The premium is always positive or zero with respect to long-term Treasuries. It may be negative for short-term Treasuries when short-term productivity outpaces medium and long run trends. Consequently: (4) Treasury yields are mostly determined in reference to the required yield and the business cycle risk premium; (5) the yield spread is largely explained by the differential of long-term book value per share growth vs. near term growth, with possible yield curve inversions. Finally, (6) the Fed model is partially validated since both the S&P 500 forward earnings yield and the ten-year Treasury yield are determined by a common factor: the required yield.     

Estimating the Equity Risk Premium and Expected Equity Rates of Return: The Case of Canada

It is common to use the average excess return of equities over bonds estimated over long time periods as an expected equity risk premium on the grounds that going back far enough covers most possible economic scenarios. But although this data is useful in guiding the exercise of judgment, it cannot substitute for judgment. Adding more years of data to the near century of Canadian stock and bond returns that inform today's estimate of the equity risk premium will not produce a “random walk” for a simple reason: the historic bond series is the result of a specific historic monetary policy. This is particularly true of and important for the case of Canada, where today's very low current bond yields reflect the emergence of the Canadian dollar as a reserve currency as well as the impact of unconventional monetary policy elsewhere. After analyzing the historic record of the Canadian equity risk premium and noting the need for adjustments when this premium is applied to the current anomalously low Canadian long‐term bond yields, the author reaches the following conclusions:

• The historic Canadian equity risk premium is approximately 5.0% (based on arithmetic returns), which is slightly lower than the roughly 6.0% value for the U.S.
• The historic equity risk premium has not been constant because of obvious changes in the Canadian bond market. To some extent, the huge cycle in which bond yields began their increase from the 4.0% level starting in 1957, when markets were liberalized, and then fell back to the 4.0% level in 2007‐2008 completed an adjustment to changes in fiscal versus monetary policy. However, in 2016, average long Canada bond yields dropped to an anomalously low 1.8%, which is below the long‐term inflation target of the Bank of Canada, and have barely recovered since. It is difficult to view this as an equilibrium rate determined by private investors.
• Of the drop in bond yields, about 0.50% is unique to Government of Canada bonds as they became attractive to sovereign investors as a rare AAA‐rated issuer.
• Using an indicator variable for the post‐2010 years, a simple regression analysis indicates that current long Canada bond yields should be about 2.75% higher but for the recent changes. And for 2018, this means that the 2.35% average long Canada bond yield should have been about 5.0%. Apart from the impact of higher government deficits, this is consistent with average yields before the 2008 financial crisis.
• Adding an adjusted 5.0% long Canada bond yield to the historic equity risk premium in Canada of 4.50% gives 9.50% for the cost of the overall equity market or, given the Bank of Canada's target inflation rate of 2.0%, a real equity return of 7.5%, both slightly higher than the long‐run averages.

In sum, the conventional practice of adding a historic market risk premium to the current low Canada long bond yields would impart a sharp downward bias to current equity cost estimates; use of this method would not be appropriate until long Canada bond yields increase to at least the 4.0% level.     

Time-Varying Variance Risk Premium and the Predictability of Chinese Stock Market Return

A number of studies have shown that the variance risk premium (VRP), defined as the difference between risk-neutral and physical expected variances, has strong predictive power for the excess stock market return, and this predictability peaks at 3- to 6-month prediction horizons. However, little research presents empirical evidences for Chinese stock market due to the absence of option market. Under general equilibrium asset pricing framework, this article estimates time-varying VRP using the Chinese stock market data. We find that the estimated VRP predicts the excess Chinese stock market return, and this forecasting power is stronger at 4- and 5-month horizons, which is consistent with the findings of existing literature.     

Stock liquidity premium with stochastic price impact and exogenous trading strategy

This paper provides a model which helps explain the variability of stock liquidity premium. Liquidity is modelled as a time-varying price impact and includes both permanent as well as temporary price impacts. Liquidity premium is defined as an additional expected return that stock should yield to compensate an investor for the potential loss of wealth utility caused by price impact costs. The numerical results presented show that liquidity premium varies with expected net stock return, return volatility and, to a lesser extent, with returns on risk-free bonds. Liquidity premium is a growing and convex function of liquidity costs, and temporary price impact has a more severe effect on liquidity premium than the permanent one.     

Determinants of market-assessed sovereign risk: Economic fundamentals or market risk appetite?

This paper examines the determinants of the market-assessed sovereign risk premium, measured by the Brady bond stripped yield spread. Our study shows that, while standard economic fundamentals of a sovereign significantly affect the bond yield spread, the market's attitude towards risk is another important determinant. We construct a measure of the market's attitude towards risk called the risk appetite index (RAI), and find that for comparable changes in all the economic variables the RAI has a relatively large impact on the Brady bond yield spread. Our results explain why there is contagion in the Brady bond market and why often there is a divergence between the market's perception of the country risk premium and published ratings on sovereign creditworthiness.     

The Volatility of Bid‐Ask Spreads

This study tests whether the volatility of bid‐ask spreads is positively related to expected returns. After controlling for market‐risk factors, we find that the average risk‐adjusted excess return for stocks in the highest spread volatility quintile is around 50 basis points per month. In a variety of multivariate tests, we find robust evidence of a return premium associated with spread volatility that is both statistically significant and economically meaningful. Our results are robust to controls for a variety of stock characteristics, different tick‐size regimes, and other measures of liquidity volatility.     

Tests of the foreign exchange risk premium using the expected second moments implied by option pricing

This paper utilizes the second moment expectations implied by currency option pricing to demonstrate that these expectations are systematically related to expected return differentials across assets denominated in different currencies. Because the measured deviations from uncovered interest rate parity are tied to variables which theory links to the risk premium, the results provide substantial evidence that a risk premium does indeed exist, as opposed to the alternative of a violation of rational expectations. However, like previous attempts, the data do not support an explicit mean-variance formulation of the risk premium.     

The Risk Microstructure of Corporate Bonds: A Case Study from the German Corporate Bond Market

This article presents joint econometric analysis of interest rate risk, issuer‐specific risk (credit risk) and bond‐specific risk (liquidity risk) in a reduced‐form framework. We estimate issuer‐specific and bond‐specific risk from corporate bond data in the German market. We find that bond‐specific risk plays a crucial role in the pricing of corporate bonds. We observe substantial differences between different bonds with respect to the relative influence of issuer‐specific vs. bond‐specific spread on the level and the volatility of the total spread. Issuer‐specific risk exhibits strong autocorrelation and a strong impact of weekday effects, the level of the risk‐free term structure and the debt to value ratio. Moreover, we can observe some impact of the stock market volatility, the respective stock's return and the distance to default. For the bond‐specific risk we find strong autocorrelation, some impact of the stock market index, the stock market volatility, weekday effects and monthly effects as well as a very weak impact of the risk‐free term structure and the specific stock's return. Altogether, the determinants of the spread components vary strongly between different bonds/issuers.     

Asymmetric risk premium in value and growth stocks

There are two competing explanations for the existence of a value premium, a rational market risk explanation, whereby value stocks are inherently more risky than growth stocks, and a market over-reaction hypothesis, where agents overstate future returns on growth stock. Using asymmetric GARCH-M models this paper tests the predictions of the two hypotheses. Specifically, examining whether returns exhibit a positive (negative) risk premium resulting from a negative (positive) shock and the relative size of any premium. The results of the paper suggest that following a shock, volatility and expected future volatility are heightened, leading to a rise in required rates of return which depresses current prices. Further, these effects are heightened for value stock over growth stock and for negative shocks over positive shocks. Thus, in support of the rational risk interpretation, with a volatility feedback explanation for predictive volatility asymmetry.     

Mortgage timing

We study how the term structure of interest rates relates to mortgage choice at both household and aggregate levels. A simple utility framework of mortgage choice points to the long-term bond risk premium as distinct from the yield spread and the long yield as a theoretical determinant of mortgage choice: when the bond risk premium is high, fixed-rate mortgage payments are high, making adjustable-rate mortgages more attractive. We confirm empirically that the bulk of the time variation in both aggregate and loan-level mortgage choice can be explained by time variation in the bond risk premium, whether bond risk premia are measured using forecasters’ data, a vector autoregressive (VAR) term structure model, or a simple household decision rule based on adaptive expectations. The household decision rule moves in lock-step with mortgage choice, lending credibility to a theory of strategic mortgage timing by households.     

Hard markets,hard times: On the inefficiency of the CAT bond market

This study explores the existence of inefficiencies in catastrophe (CAT) bond secondary markets by investigating the impact of sponsor characteristics on the CAT bond premium. We show that the CAT bond market does not satisfy the demand for catastrophe risk transfer efficiently by revealing a significant effect of sponsor-related factors on the CAT bond premium. This inefficiency is particularly surprising given that a CAT bond isolates the insured risk from other sponsor-related risks through a special purpose vehicle. Remarkably, this inefficiency is even present among non-indemnity CAT bonds, which determine the payout through a mechanism that is exogenous to the sponsor. Our findings also reveal that sponsor-related pricing inefficiencies vary over time and are more relevant during hard and neutral phases compared to soft market phases. Among the sponsor-related determinants of the CAT bond premium are the sponsor's tenure, market coverage, rating, credit default swap spread, and his ability to issue innovative “on the run” CAT bonds.     

Credit Spread Changes and Equity Volatility: Evidence from Daily Data

We investigate the determinants of daily changes in credit spreads in the U.S. corporate bond market. Using a sample of liquid investment grade and high‐yield bonds, we show that both systematic bond and stock market factors as well as idiosyncratic equity market factors affect changes in the yield spread at the daily frequency. In particular, we find that increase in stock market volatility has a positive effect on changes in the spread of corporate bonds over the corresponding Treasuries beyond that captured by standard term structure variables. Our results show that there is an almost contemporaneous inverse relationship between changes in the bond yield spread and the stock return of the issuing firm.     

Explaining the idiosyncratic volatility puzzle using Stochastic Discount Factors

I use Stochastic Discount Factors to examine the sources of the idiosyncratic volatility premium. I find that non-zero risk aversion and firms’ non-systematic coskewness determine the premium on idiosyncratic volatility risk. The firm’s non-systematic coskewness measures the comovement of the asset’s volatility with the market return. When I control for the non-systematic coskewness factor, I find no significant relation between idiosyncratic volatility and stock expected returns. My results are robust across different sample periods and firm characteristics.     

The Variation of Economic Risk Premiums in Real Estate Returns

We examine the predictable components of returns on stocks, bonds, and real estate investment trusts (REITs). We employ a multiple-beta asset pricing model and find that there are varying degrees of predictability among stocks, bonds, and REITs. Furthermore, we find that most of the predictability of returns is associated with the economic variables employed in the asset pricing model. The stock market risk premium is highly important in capturing the predictable variation in stock portfolios, and the bond market risk premiums (term and risk structure of interest rates) are important in capturing the predictable variation in bond portfolios. For REITs, however, both the stock and bond market risk premiums capture the predictable variation in returns. REITs have comparable return predictability to stock portfolios. We conclude that there is an important economic risk premium for REITs that are not captured by traditional multiple-beta asset pricing models.     

Cross-sectional dispersion and expected returns

This study investigates whether the cross-sectional dispersion of stock returns, which reflects the aggregate level of idiosyncratic risk in the market, represents a priced state variable. We find that stocks with high sensitivities to dispersion offer low expected returns. Furthermore, a zero-cost spread portfolio that is long (short) in stocks with low (high) dispersion betas produces a statistically and economically significant return. Dispersion is associated with a significantly negative risk premium in the cross section (–1.32% per annum) which is distinct from premia commanded by alternative systematic factors. These results are robust to stock characteristics and market conditions.     

How Does Information Quality Affect Stock Returns?

Using a simple dynamic asset pricing model, this paper investigates the relationship between the precision of public information about economic growth and stock market returns. After fully characterizing expected returns and conditional volatility, I show that (i) higher precision of signals tends to increase the risk premium, (ii) when signals are imprecise the equity premium is bounded above independently of investors' risk aversion, (iii) return volatility is U-shaped with respect to investors' risk aversion, and (iv) the relationship between conditional expected returns and conditional variance is ambiguous.     

The relation between stock returns and short-term interest rates

This study examines the relation between the expected returns on common stocks and short-term interest rates. Using a two-factor model of stock returns, we show that the expected returns on common stocks are systematically related to the market risk and the interest-rate risk, which are estimated as the sensitivity of common-stock excess returns to the excess return on the equally weighted market index and to the federal fund premium, respectively. We find that the interest-rate risk for small firms is a significant source of investors' portfolio risk, but is not properly reflected in the single-factor market risk. We also find that the interest-rate risk for large firms is “negative” in the sense that the market risk estimated from the single-factor model overstates the true risk of large firms. An application of the Fama-MacBeth methodology indicates that the interest-rate risk premium as well as the market's risk premium are significant, implying that both the market risk and the interest-rate risk are priced. We show that the interest-rate risk premium explains a significant portion of the difference in expected returns between the top quintile and the bottom quintile of the NYSE and AMEX firms. We also show that the turn-of-the-year seasonal is observed for the interest-rate risk premium; however, the risk premium for the rest of the year is still significant, although small in mangitude.