Diversification and the Optimal Construction of Basis Portfolios

Nontrivial diversification possibilities arise when a factor model describes security returns. In this paper, we provide a comprehensive examination of the merits of various strategies for constructing basis portfolios that are, in principle, highly correlated with the common factors underlying security returns. Three main conclusions emerge from our study. First, increasing the number of securities included in the analysis dramatically improves basis portfolio performance. Our results indicate that factor models involving 750 securities provide markedly superior performance to those involving 30 or 250 securities. Second, comparatively efficient estimation procedures such as maximum likelihood and restricted maximum likelihood factor analysis (which imposes the APT mean restriction) significantly outperform the less efficient instrumental variables and principal components procedures that have been proposed in the literature. Third, a variant of the usual Fama-MacBeth portfolio formation procedure, which we call the minimum idiosyncratic risk portfolio formation procedure, outperformed the Fama-MacBeth procedure and proved equal to or better than more expensive quadratic programming procedures.

Testing the statistical significance of sector & regional diversification

The question as to whether it is better to diversify a real estate portfolio within a property type across the regions or within a region across the property types is one of continuing interest for academics and practitioners alike. The current study, however, is somewhat different from the usual sector/regional analysis taking account of the fact that holdings in the UK real estate market are heavily concentrated in a single region, London. As a result this study is designed to investigate whether a real estate fund manager can obtain a statistically significant improvement in risk/return performance from extending out of a London based portfolio into firstly the rest of the South East of England and then into the remainder of the UK, or whether the manger would be better off staying within London and diversifying across the various property types. The results indicating that staying within London and diversifying across the various property types may offer performance comparable with regional diversification, although this conclusion largely depends on the time period and the fund manager’s ability to diversify efficiently

Real estate portfolio construction and estimation risk

The use of MPT in the construction real estate portfolios has two serious limitations when used in an ex-ante framework: (1) the intertemporal instability of the portfolio weights and (2) the sharp deterioration in performance of the optimal portfolios outside the sample period used to estimate asset mean returns. Both problems can be traced to wide fluctuations in sample means Jorion (1985). Thus the use of a procedure that ignores the estimation risk due to the uncertain in mean returns is likely to produce sub-optimal results in subsequent periods. This suggests that the consideration of the issue of estimation risk is crucial in the use of MPT in developing a successful real estate portfolio strategy. Therefore, following Eun & Resnick (1988), this study extends previous ex-ante based studies by evaluating optimal portfolio allocations in subsequent test periods by using methods that have been proposed to reduce the effect of measurement error on optimal portfolio allocations

Asset allocation, cross-class correlation and the structure of property returns

Practical applications of portfolio optimisation tend to proceed on a “top down” basis where funds are allocated first at asset class level (between, say, bonds, cash, equities and real estate) and then, progressively, at sub-class level (within property to sectors, office, retail, industrial for example). While there are organisational benefits from such an approach, it can potentially lead to sub-optimal allocations when compared to a “global” or “side-by-side” optimisation. This will occur where there are correlations between sub-classes across the asset divide that are masked in aggregation – between, for instance, City offices and the performance of financial services stocks. This paper explores such sub-class linkages using UK monthly stock and property data. Exploratory analysis using clustering procedures and factor analysis suggests that property performance and equity performance are distinctive: there is little persuasive evidence of contemporaneous or lagged sub-class linkages. Formal tests of the equivalence of optimised portfolios using top-down and global approaches failed to demonstrate significant differences, whether or not allocations were constrained. While the results may be a function of measurement of market returns, it is those returns that are used to assess fund performance. Accordingly, the treatment of real estate as a distinct asset class with diversification potential seems justified

Private equity-, stock- and mixed asset-portfolios: a bootstrap approach to determine performance characteristics, diversification benefits and optimal portfolio allocations : [Version: December 2003]

In this article, we investigate risk return characteristics and diversification benefits when private equity is used as a portfolio component. We use a unique dataset describing 642 US-American portfolio companies with 3620 private equity investments. Information about precisely dated cash flows at the company level enables for the first time a cash flow equivalent and simultaneous investment simulation in stocks, as well as the construction of stock portfolios for benchmarking purposes. With respect to the methodology involved, we construct private equity, stock-benchmark and mixed-asset portfolios using bootstrap simulations. For the late 1990s we find a dramatic increase in the extent to which private equity outperforms stock investment. In earlier years private equity was underperforming its stock benchmarks. Within the overall class of private equity, returns on earlier private equity investment categories, like venture capital, show on average higher variations and even higher rates of failure. It is in this category in particular that high average portfolio returns are generated solely by the ability to select a few extremely well performing companies, thus compensating for lost investments. There is a high marginal diversifiable risk reduction of about 80% when the portfolio size is increased to include 15 investments. When the portfolio size is increased from 15 to 200 there are few marginal risk diversification effects on the one hand, but a large increase in managing expenditure on the other, so that an actual average portfolio size between 20 and 28 investments seems to be well balanced. We provide empirical evidence that the non-diversifiable risk that a constrained investor, who is exclusively investing in private equity, has to hold exceeds that of constrained stock investors and also the market risk. From the viewpoint of unconstrained investors with complete investment freedom, risk can be optimally reduced by constructing mixed asset portfolios. According to the various private equity subcategories analyzed, there are big differences in optimal allocations to this asset class for minimizing mixed-asset portfolio variance or maximizing performance ratios. We observe optimal portfolio weightings to be between 3% and 65%

The relative importance of sectors v's regions in determining property returns

A number of studies have investigated the benefits of sector versus regional diversification within a real estate portfolio without explicitly quantify the relative benefits of one against the other. This paper corrects this omission by adopting the approach of Heston and Rouwenhorst (1994) and Beckers, Connor and Curds (1996) on a sample of 187 property data points using annual data over the period 1981-1995. The general conclusion of which is the sector diversification explains on average 22% of the variability of property returns compared with 8% for administratively defined regions. A result in line with previous work. Implying that sector diversification should be the first level of analysis in constructing and managing the real estate portfolio. However, unlike previous work functionally defined regions provide less of an explanation of regional diversification than administrative regions. Which may be down to the weak definition of economic regions employed in this study

Multi-bank loan pool contracts

EFM classification: 330, 350We show that multi-bank loan pools improve the risk-return profile of banks’ loan business. Banks write simple contracts on the proceeds from pooled loan portfolios, taking into account the free-rider problems in joint loan production. Thus, banks benefit greatly from diversifying credit risk while limiting the efficiency loss due to adverse incentives. We present calibration results that the formation of loan pools reduce the volatility in default rates, proxying for credit risk, of participating banks’ loan portfolios by roughly 70% in our sample. Under reasonable assumptions, the gain in return on equity (in certainty equivalent terms) is around 20 basis points annually

Portfolio size and the reduction of dispersion: the case of the United Kingdom commercial real estate market

This paper investigates the potential benefits and limitations of equal and value-weighted diversification using as the example the UK institutional property market. To achieve this it uses the largest sample (392) of actual property returns that is currently available, over the period 1981 to 1996. To evaluate these issues two approaches are adopted; first, an analysis of the correlations within the sectors and regions and secondly simulations of property portfolios of increasing size constructed both naively and with value-weighting. Using these methods it is shown that the extent of possible risk reduction is limited because of the high positive correlations between assets in any portfolio, even when naively diversified. It is also shown that portfolios exhibit high levels of variability around the average risk, suggesting that previous work seriously understates the number of properties needed to achieve a satisfactory level of diversification. The results have implications for the development and maintenance of a property portfolio because they indicate that the achievable level of risk reduction depends upon the availability of assets, the weighting system used and the investor’s risk tolerance