Real Exchange Rate and External Balance: How Important Are Price Deflators?

This paper contrasts real effective exchange rate (REER) measures based on different deflators (consumer price index, GDP deflator, and unit labor cost) and discusses potential implications for the link—or lack thereof—between the REER and the external balance. We begin by comparing the evolution of different measures of REER to confirm that the choice of deflator plays a significant role in REER movements. A subsequent empirical investigation based on 35 developed and emerging market economies over 1995–2017 yields comprehensive and robust evidence that only the REER deflated by unit labor cost exhibits contemporaneous patterns consistent with the expenditure-switching mechanism. Finally, we show that a standard open-economy model with nominal rigidities and trade in intermediate goods is able to generate these aforementioned patterns.     

Convex duality and Orlicz spaces in expected utility maximization

In this paper, we report further progress toward a complete theory of state‐independent expected utility maximization with semimartingale price processes for arbitrary utility function. Without any technical assumptions, we establish a surprising Fenchel duality result on conjugate Orlicz spaces, offering a new economic insight into the nature of primal optima and providing a fresh perspective on the classical papers of Kramkov and Schachermayer. The analysis points to an intriguing interplay between no‐arbitrage conditions and standard convex optimization and motivates the study of the fundamental theorem of asset pricing for Orlicz tame strategies.     

Regional price deflators in Poland: evidence from NUTS-2 and NUTS-3 regions

This paper analyzes regional price differentials in Poland at the NUTS-2 and NUTS-3 levels. It applies unique raw-price data and calculates regional purchasing power parity (PPP) deflators for the 16 NUTS-2 regions. It then estimates PPP deflators for the 66 NUTS-3-level regions by applying the multiple imputation approach. Finally, it verifies whether these are intra- or interregional price inequalities that have a greater influence on the overall price inequality level. It is found that the price levels are significantly higher than the average in the better-developed regions and lower in the lagging ones. It is also found that it is the intra- rather than the interregion differentials that influence more the overall inequality level.     

Poverty Lines as Context Deflators: A Method to Account for Regional Diversity with Application to the Democratic Republic of Congo

This paper proposes a particular methodology to render budget data more comparable over highly diverse regions. More specifically, a set of regional poverty lines will be derived and employed as deflators to correct household expenditures for spatial differences in prices and needs. The quality of these deflators depends on the extent to which the underlying poverty lines adhere to the principles of consistency and specificity. Central to reconciling both principles in practice is our pursuit for austerity in setting poverty thresholds as well as the view that differences in social norms mainly reflect differences in social inclusion needs. The particularity of the proposed method compared to standard practice lies in the combination of: (i) the pronounced subdivision in socio‐economic strata; (ii) the use of a differential calorie threshold per sector; (iii) the introduction of protein intake; (iv) the derivation of a minimal house rent; and (v) the use of an austere non‐food/non‐housing allowance. The impact of this method is illustrated using a budget survey of the Democratic Republic of Congo.     

A supermartingale relation for multivariate risk measures

The equivalence between multiportfolio time consistency of a dynamic multivariate risk measure and a supermartingale property is proven. Furthermore, the dual variables under which this set-valued supermartingale is a martingale are characterized as the worst-case dual variables in the dual representation of the risk measure. Examples of multivariate risk measures satisfying the supermartingale property are given. Crucial for obtaining the results are dual representations of scalarizations of set-valued dynamic risk measures, which are of independent interest in the fast growing literature on multivariate risks.     

CONSTRAINED OPTIMIZATION WITH RESPECT TO STOCHASTIC DOMINANCE: APPLICATION TO PORTFOLIO INSURANCE

We are concerned with a classic portfolio optimization problem where the admissible strategies must dominate a floor process on every intermediate date (American guarantee). We transform the problem into a martingale, whose aim is to dominate an obstacle, or equivalently its Snell envelope. The optimization is performed with respect to the concave stochastic ordering on the terminal value, so that we do not impose any explicit specification of the agent's utility function. A key tool is the representation of the supermartingale obstacle in terms of a running supremum process. This is illustrated within the paper by an explicit example based on the geometric Brownian motion.     

NO-FREE-LUNCH EQUIVALENCES FOR EXPONENTIAL LÉVY MODELS UNDER CONVEX CONSTRAINTS ON INVESTMENT

We provide equivalence of numerous no-free-lunch type conditions for financial markets where the asset prices are modeled as exponential Lévy processes, under possible convex constraints in the use of investment strategies. The general message is the following: if any kind of free lunch exists in these models it has to be of the most egregious type, generating an increasing wealth. Furthermore, we connect the previous to the existence of the numéraire portfolio , both for its particular expositional clarity in exponential Lévy models and as a first step in obtaining analogues of the no-free-lunch equivalences in general semimartingale models, a task that is taken on in Karatzas and Kardaras (2007) .     

DYNAMIC DEFAULTABLE TERM STRUCTURE MODELING BEYOND THE INTENSITY PARADIGM

The two main approaches in credit risk are the structural approach pioneered by Merton and the reduced‐form framework proposed by Jarrow and Turnbull and by Artzner and Delbaen. The goal of this paper is to provide a unified view on both approaches. This is achieved by studying reduced‐form approaches under weak assumptions. In particular, we do not assume the global existence of a default intensity and allow default at fixed or predictable times, such as coupon payment dates, with positive probability. In this generalized framework, we study dynamic term structures prone to default risk following the forward‐rate approach proposed by Heath, Jarrow, and Morton. It turns out that previously considered models lead to arbitrage possibilities when default can happen at a predictable time. A suitable generalization of the forward‐rate approach contains an additional stochastic integral with atoms at predictable times and necessary and sufficient conditions for an appropriate no‐arbitrage condition are given. For efficient implementations, we develop a new class of affine models that do not satisfy the standard assumption of stochastic continuity. The chosen approach is intimately related to the theory of enlargement of filtrations, for which we provide an example by means of filtering theory where the Azéma supermartingale contains upward and downward jumps, both at predictable and totally inaccessible stopping times.     

MEAN‐VARIANCE POLICY FOR DISCRETE‐TIME CONE‐CONSTRAINED MARKETS: TIME CONSISTENCY IN EFFICIENCY AND THE MINIMUM‐VARIANCE SIGNED SUPERMARTINGALE MEASURE

The discrete‐time mean‐variance portfolio selection formulation, which is a representative of general dynamic mean‐risk portfolio selection problems, typically does not satisfy time consistency in efficiency (TCIE), i.e., a truncated precommitted efficient policy may become inefficient for the corresponding truncated problem. In this paper, we analytically investigate the effect of portfolio constraints on the TCIE of convex cone‐constrained markets. More specifically, we derive semi‐analytical expressions for the precommitted efficient mean‐variance policy and the minimum‐variance signed supermartingale measure (VSSM) and examine their relationship. Our analysis shows that the precommitted discrete‐time efficient mean‐variance policy satisfies TCIE if and only if the conditional expectation of the density of the VSSM (with respect to the original probability measure) is nonnegative, or once the conditional expectation becomes negative, it remains at the same negative value until the terminal time. Our finding indicates that the TCIE property depends only on the basic market setting, including portfolio constraints. This motivates us to establish a general procedure for constructing TCIE dynamic portfolio selection problems by introducing suitable portfolio constraints.     

Neural Networks and Empirical Research in Accounting

This article seeks to provide an overview of the potential role of neural network (connectionist) methodology in empirical accounting research. It highlights how the accounting task domain differs substantially from those for which neural network techniques were originally developed. A non-technical overview of neural network methodology is given, along with guidelines to help accounting researchers interested in applying these new tools to recognise the potential dangers and strengths underlying their use. An illustrative example is provided. The paper suggests research areas in accounting where neural network approaches could make a potential contribution. Explicit recommendations for prospective authors are made.