Principles of stochastic dynamic optimization in resource management: the continuous-time case

A wide range of problems in economics, agriculture, and natural resource management have been analyzed using continuous-time optimal control models, where the state variables change over time in a stochastic manner. Using a firm-level investment model and a model of environmental degradation, this paper provides a concise introduction to continuous-time stochastic control techniques. The process used to derive the differential of a stochastic process is stressed and, in turn, is used to explain Ito's lemma, Bellman's equation, the Hamilton-Jacobi equation, the maximum principle, and the expected dynamics of choice variables. A basic extension of the dynamic duality literature is also provided, where the Hamilton-Jacobi equation is used to derive a stochastic and dynamic analogue of Hotelling's lemma.     

SUPPLY-MAXIMISING AND VARIATION-MINIMISING REPLACEMENT CYCLES OF PERENNIAL CROPS AND SIMILAR ASSETS: THEORY ILLUSTRATED BY COCONUT CULTIVATION

The paper argues that maximum sustainable yields rather than net present values often need to be considered for policy and identifies the length of the replacement cycle required for maximum sustainable yield or supply in multi-point or interval output time-phased production conditions, such as apply to perennial crops and to similar productive processes. It enables point-input point-output models which have been well explored (for instance, for forestry) to be treated as special cases. A virtue of the analysis is its use of a simple technical relationship to determine the replacement rate of a perennial crop to maximise sustainable yield. The analysis is illustrated by an empirical example drawn for the cultivation of the Sri Lankan ‘tall’ variety of coconut.     

Academies 2 – The New Batch: The Changing Nature of Academy Schools in England

The English education system has undergone large‐scale restructuring through the introduction of academy schools. The most salient feature of these schools is that, despite remaining part of the state sector, they operate with more autonomy than the predecessors they replaced. Two distinct periods of academy school introduction have taken place, under the auspices of different governments. The first batch was initiated in the 2002–03 school year by the Labour government of the time, and was a school improvement programme directly aimed at turning around badly performing schools. The second batch involved a mass academisation process following the change of government in May 2010 and the Academies Act of that year, which resulted in increased heterogeneity of new academies. This paper compares the two batches of introduction with the aim of getting a better understanding of their similarities and differences, and their importance for education policy. To do so, we study what types of schools were more likely to change to academy status in the two programmes, and the impact of this change on the quality of new pupil enrolments into the new types of school. Whilst we do point out some similarities, these are the exception rather than the norm. For the most part, our analysis reveals a number of marked dissimilarities between the two programmes, in terms of both the characteristics of schools that became academies and the changes in pupil intakes that occurred post‐conversion.     

Can VPIN forecast geopolitical events? Evidence from the 2014 Crimean Crisis

We study the recent Crimean Crisis and the sequence of outcomes that led to the intervention by the Russian Army, which directly affected equity prices in Russia, to investigate how informed traders may have used their advantage to trade prior to the moment markets fell. We compute the Volume-synchronized Probability of Informed Trading (VPIN) for the Russian RTS equity index and for individual stocks, documenting that levels of informed trading increased considerably between one and three trading days before market prices reflected the invasion. We also investigate the predictive power of the cumulative distribution of VPIN on future stock prices, showing a statistically significant (negative) relation during the period of elevated tensions between Russia and Ukraine. Last, we investigate the levels of VPIN measured for global depositary receipts of Russian firms, documenting a similar increasing pattern prior to the invasion date but generally subsequent to the spikes obtained from the corresponding securities locally traded in Russia. Overall, our results provide additional support for the use of VPIN as a tool for monitoring the likelihood of undesirable geopolitical events.     

Effect of guideline implementation on costs of hand hygiene

Hands of health care personnel frequently serve as vectors for the transmission of organisms between patients and are also a major reservoir for pathogens with antimicrobial resistance. Hand hygiene is one effective strategy to reduce health care associated infections. The purposes of this study were to (a) compare the costs of hand hygiene in hospitals with high and low hand hygiene compliance as well as high and low frequency of alcohol hand rub use; and (b) examine associations between hospital characteristics and hand hygiene compliance as well as frequency of alcohol hand rub use. Nursing and health care policy leaders should look for ways to promote sustained adherence to hand hygiene recommendations.     

More equal but not so fair: an analysis of Brazilian income distribution from 1995 to 2009

This study measures unfair inequality in Brazil between 1995 and 2009. To achieve that, we used the statistical tool developed by Almås et al. (J Public Econ 95:488–499, 2011) and the concept of “responsibility-sensitive” fairness proposed by Bossert (Math Soc Sci 29:1–17, 1995), Konow (J Econ Behav Organ 31(1):13–35, 1996) and Cappelen and Tungodden (Fairness and the proportionality principle, Discussion paper SAM 31/2007. Norwegian School of Economics and Business Administration, 2007). The results indicate that the fairness level in Brazil remained unchanged throughout the analyzed period.