WWTP dynamic disturbance modelling--an essential module for long-term benchmarking development.

Intensive use of the benchmark simulation model No. 1 (BSM1), a protocol for objective comparison of the effectiveness of control strategies in biological nitrogen removal activated sludge plants, has also revealed a number of limitations. Preliminary definitions of the long-term benchmark simulation model No. 1 (BSM1_LT) and the benchmark simulation model No. 2 (BSM2) have been made to extend BSM1 for evaluation of process monitoring methods and plant-wide control strategies, respectively. Influent-related disturbances for BSM1_LT/BSM2 are to be generated with a model, and this paper provides a general overview of the modelling methods used. Typical influent dynamic phenomena generated with the BSM1_LT/BSM2 influent disturbance model, including diurnal, weekend, seasonal and holiday effects, as well as rainfall, are illustrated with simulation results. As a result of the work described in this paper, a proposed influent model/file has been released to the benchmark developers for evaluation purposes. Pending this evaluation, a final BSM1_LT/BSM2 influent disturbance model definition is foreseen. Preliminary simulations with dynamic influent data generated by the influent disturbance model indicate that default BSM1 activated sludge plant control strategies will need extensions for BSM1_LT/BSM2 to efficiently handle 1 year of influent dynamics.     

Passive Investment Strategies and Efficient Markets

This paper presents the case for and the evidence in favour of passive investment strategies and examines the major criticisms of the technique. I conclude that the evidence strongly supports passive investment management in all markets—small–capitalisation stocks as well as large–capitalisation equities, US markets as well as international markets, and bonds as well as stocks. Recent attacks on the efficient market hypothesis do not weaken the case for indexing.     

Ag econ angst crisis revisited

The present paper was inspired by and is a response to the Rola-Rubzen, Hardaker and Dillon paper 'Agricultural economists and world poverty: progress and prospects' (Rola-Rubzen et al. 2001). It is agreed that the position of agricultural economists in foreign aid and poverty programs has declined over recent decades. Such a feeling of guilt and remorse expressed by the above authors does indeed create considerable 'angst'. A major reason for this state of affairs lies in 'the flavour of the month' approach of the development agencies. These include women in development, gender-based farming systems research, household nutrition and food security, people participation, and targeting the poorest of the poor. These fads have driven disciplinary considerations to the wall and the more widely-defined objectives have reduced the drive for economic efficiency. We argue there is still a place for better designed and delivered assistance programs within the wider framework of assistance that has become fashionable. Greater application of institutional principles in both the political processes associated with assistance and the implementation agencies would improve the outcomes of many projects. Particular attention would need to be given to the interface between the development agencies and recipient governments. The present paper picks up on the market failure aspects of agriculture's rather poor contribution to development, and develops a wider perspective in terms of the new institutional economics and a continuing role for the agricultural economist.     

EDITORIAL: TAX REFORM AND SIMPLIFICATION

Major tax reform to simplify the UK tax system is possible. Merging income taxes, social security taxes and corporation tax into only a single flat-rate of tax on all incomes would be a radical start. Avoiding taxes on income and expenditure which are 'too high' requires major reductions in government spending, mainly on the welfare state. Given the political will, over a period of years we really can hugely improve the UK tax system.     

Lake Chivero: A management case study

Lake Chivero in Zimbabwe was shown to be hypereutrophic. Historical data showed that the eutrophication process had been arrested in the late 1970s. However, a combination of poor planning, multiplicity of jurisdiction, mismatch between rate of urbanization and waste management investment, recent changes in the local climate and a permissive, immature political system that called for no public accountability resulted in environmental management breakdown leading to hypereutrophication of the lake. The case of Lake Chivero is presented as an example of a wider global issue regarding the status of environmental management in competition with other priorities in emerging democracies.     

Adverse Selection and the Decline in Private Health Insurance Coverage in Australia: 1989–95

The decline in private health insurance coverage over the period 1989–95 is analysed using the ABS National Health Surveys. Individuals' health status and health risk behaviours are found to be significant determinants of their decision to purchase private health insurance. At a point in time, the pool of the insured is very heterogeneous, with a mix of both good and bad health risks. It is found that the decline in insurance coverage over the period 1989–95 coincided with an increase in the degree of 'adverse selection' within the insured population.     

Operation of the dam of the Bureiskaya HPP during filling of the reservoir

Operation of the dam in a transitional mode is described. __________ Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 1, January 2006, pp. 8–15.     

Exploring the Intensive and Extensive Margins of World Trade

World trade evolves at two margins. Where a bilateral trading relationship already exists it may increase through time (intensive margin). But trade may also increase if a trading bilateral relationship is newly established between countries that have not traded with each other in the past (extensive margin). We provide an empirical dissection of post–World War II growth in manufacturing world trade along these two margins. We propose a “corner-solutions version” of the gravity model to explain movements on both margins. A Tobit estimation of this model resolves the so-called “distance puzzle”. It also finds more convincing evidence than recent literature that WTO-membership enhances trade. JEL no. F12, F15