Optimal granularity for portfolio choice

Many optimization-based portfolio rules fail to beat the simple 1/N rule out-of-sample because of parameter uncertainty. In this paper we suggest a grouping strategy in which we first form groups of equally weighted stocks and then optimize over the resulting groups only. This strategy aims at balancing the trade-off between the benefits from optimization and the losses from estimation risk. We rely on Monte-Carlo simulations to illustrate the performance of the strategy, and we derive the optimal group size for a simplified setup. Furthermore, we show that estimation risk also has an impact via the criterion by which the assets are sorted into groups (like the expected excess returns or betas), but does not negate the grouping approach. We relate our work to linear asset pricing models, and we conduct out of sample back-tests in order to confirm the validity of our grouping strategy empirically.     

Is econometrics useful for private policy making? A case study of replacement policy at an auto rental company

The goal of this paper is to illustrate the potential usefulness of econometrics as a tool to assist private policy makers. We provide a case study and detailed econometric analysis of the automobile replacement policy adopted by a large car rental company. Unlike public policy making–where the benefits from using econometric models and “science-based” approaches to policy making are hard to quantify because the outcomes of interest are typically subjective quantities such as “social welfare”–in the case of firms there is an objective, easily quantifiable criterion for judging whether policy A is better than policy B: profits. We introduce and estimate an econometric model of the rental histories of individual cars in the company’s fleet. Via stochastic simulations, we show that the model provides a good approximation to the company’s actual operations. In particular, the econometric model is able to reproduce the extraordinarily high rates of return that the company obtains on its rental cars, with average internal rates of return between purchase and sale of approximately 50%. However, the econometric model can simulate outcomes under a range of counterfactual vehicle replacement policies. We use the econometric model to simulate the profitability of an alternative replacement policy under pessimistic assumptions about the rate maintenance costs would increase and rental rates would have to be decreased if the company were to keep its rental cars longer than it does under the status quo. Depending on the vehicle type, we find that the company’s expected discounted profits would be between 6% to over 140% higher under the suggested alternative operating strategy where vehicles are kept longer and rental rates of older vehicles are discounted to induce customers to rent them. The company found this analysis to be sufficiently convincing that it undertook an experiment to verify the predictions of the econometric model.     

Gains from international monetary policy coordination: Does it pay to be different?

In a two country world where each country has a traded and a non-traded sector and each sector has sticky prices, optimal independent policy in general cannot replicate the natural-rate allocations. There are potential welfare gains from coordination since the planner under a cooperating regime internalizes a terms-of-trade externality that independent policymakers overlook. If the countries have symmetric trading structures, however, the gains from coordination are quantitatively small. With asymmetric trading structures, the gains can be sizable since, in addition to internalizing the terms-of-trade externality, the planner optimally engineers a terms-of-trade bias that favors the country with a larger traded sector.     

MIND THE GAP: UNEMPLOYMENT IN THE NEW EU REGIONS

Abstract.  The paper surveys the theoretical and empirical literature on regional unemployment during transition in Central and Eastern Europe. The focus is on optimal speed of transition (OST) models and on comparison of them with the neo-classical tradition. In the typical neo-classical models, spatial differences essentially arise as a consequence of supply side constraints and institutional rigidities. Slow-growth, high-unemployment regions are those with backward economic structures and constraints on factors mobility contribute to making differences persistent. However, such explanations leave the question unanswered of how unemployment differences arise in the first place. Economic transition provides an excellent testing ground to answer this question. Pre-figuring an empirical law, the OST literature finds that the high degree of labour turnover of high unemployment regions is associated with a high rate of industrial restructuring and, consequently, that low unemployment may be achieved by implementing transition more gradually. Moreover, international trade, foreign direct investment and various agglomeration factors help explain the success of capital cities compared to peripheral towns and rural areas in achieving low unemployment. The evidence of the empirical literature on supply side factors suggests that wage flexibility in Central and Eastern Europe is not lower than in other EU countries, while labour mobility seems to reinforce rather than change the spatial pattern of unemployment.     

Value creation with Dye’s disclosure option: optimal risk-shielding with an upper tailed disclosure strategy

Dye [J Account Res 23 (1985) 123] showed that the optimal disclosure policy, when a manager is randomly endowed with perfect private information, is upper tailed, i.e., the manager only discloses firm value above an appropriate cutoff level. We interpret this strategically as an optimal exercise by management of the embedded formal option to report value. Given any disclosure cutoff level, we value the corresponding option using contingent claims analysis. It is shown that the Dye disclosure cutoff value maximizes the formal option value. We find it to be the minimum possible conditional valuation (conditioned by non-disclosure) which is thus consistent with the intuition that investors should value conservatively. We show how the Dye cutoff can be interpreted as a strike price in a ‘protective put’ which offers a shield against risk of disclosure of low value. The strategic analysis is further extended by allowing the probability level that the manager is informed to be a choice variable. We show that the manager will never choose to be perfectly endowed with information, and is likely to be more endowed than unendowed. We also present a simple worked example which shows how the total value of the firm changes once the Dye option is formally incorporated.

Optimal commodity taxation with duty-free shopping

International travellers are frequently offered the opportunity to purchase a certain quantity of goods duty-free. Individuals differ in their opportunities to benefit from duty-free shopping, and we focus on the implications of these differences for optimal commodity taxation within a version of the optimal tax model of Mirrlees (Review of Economic Studies, 38, 175–208, 1971). We show how duty-free alters the constraints on the use of commodity taxes to reduce the distortionary costs of income taxation or to reflect externalities. Beyond characterising optimal taxes in the duty-free regime, we discuss conditions under which allowing duty-free would increase or reduce social welfare.      

Optimal execution with uncertain order fills in Almgren–Chriss framework

The classical price impact model of Almgren and Chriss is extended to incorporate the uncertainty of order fills. The extended model can be recast as alternatives to uncertain impact models and stochastic liquidity models. Optimal strategies are determined by maximizing the expected final profit and loss (P&L) and various P&L-risk tradeoffs including utility maximization. Closed form expressions for optimal strategies are obtained in linear cases. The results suggest a type of adaptive volume weighted average price, adaptive percentage of volume and adaptive Almgren–Chriss strategies. VWAP and classical Almgren–Chriss strategies are recovered as limiting cases with a different characteristic time scale of liquidation for the latter.     

Measuring the unmeasurable: an application of uncertainty quantification to Treasury bond portfolios

We extract from the yield curve a new measure of fundamental economic uncertainty, based on McDiarmid’s diameter and related methods for optimal uncertainty quantification (OUQ). OUQ seeks analytical bounds on a system’s behaviour, even where aspects of the underlying data-generating process and system response function are not completely known. We use OUQ to stress test a simple fixed-income portfolio, certifying its safety—i.e. that potential losses will be ‘small’ in an appropriate sense. The results give explicit tradeoffs between: scenario count, maximum loss, test horizon, and confidence level. Unfortunately, uncertainty peaks in late 2008, weakening certification assurances just when they are needed most.     

中国商业银行最优资本水平及其调整研究——基于部分调整模型和傅里叶单位根检验的分析

采用部分调整模型和傅里叶单位根检验对中国14家上市商业银行的最优资本水平进行研究,并估计出存在最优资本水平银行的最优资本比率值和资本调整速度。研究发现,大部分上市银行均存在最优资本水平,但不同类型和资产规模的银行在最优资本比率的目标变量选择方面有所差异。平均而言,大型商业银行最优资本水平较高,股份制银行最优资本水平较低。资本调整速度在银行间差异很大,自有资金比率调整速度最快,核心资本充足率和资本充足率调整速度较慢。     

A constraint-free approach to optimal reinsurance

Reinsurance is available for a reinsurance premium that is determined according to a convex premium principle H. The first insurer selects the reinsurance coverage that maximizes its expected utility. No conditions are imposed on the reinsurer's payment. The optimality condition involves the gradient of H. For several combinations of H and the first insurer's utility function, closed-form formulas for the optimal reinsurance are given. If H is a zero utility principle (for example, an exponential principle or an expectile principle), it is shown, by means of Borch's Theorem, that the optimal reinsurer's payment is a function of the total claim amount and that this function satisfies the so-called 1-Lipschitz condition. Frequently, authors impose these two conclusions as hypotheses at the outset.