An Examination of the Interaction Between Modelling and Its Relationship with Construction Kits: Lessons from the Past and for the Future

Construction kits have played a significant part in nurturing the growth and development of the minds and manipulation-based skills of children (and adults) in formal and non-formal education settings. These kits have origins rooted in the representation of the built world and now have a diversity of form and function, including technical versions with moving parts. This article examines some of the historically based ideas that lie behind the role that kits may have in terms of physical modelling. The article traces the transformation of kits from simple bricks and blocks into more complicated pieces for space-filling and achieving the transfer of forces and motion. This transformation occurred during the Victorian era when the influence of the ideas of educationalists and, perhaps rather strangely, exponents of early aviation, played major roles in determining the diversity of forms of construction kit and modelled possibilities that are now to be seen in classrooms and homes. The article ends with a review of some of the lessons from the past and present that will need to be considered in relation to concrete modelling in schools for the future. This revised version was published online in July 2006 with corrections to the Cover Date.     

Optimal immigration, education and growth in the long run

The paper extends Manning's model on education and balanced growth to include labour immigration. Each immigration unit is assumed to consist of one skilled worker and some unskilled members. The optimal immigration policy which maximizes the per capita steady-state consumption of the host country is derived. We show that optimal immigration policy can reduce the steady-state skilled labour ratio. More interesting still, contrary to the widespread belief that immigration of skilled workers hurts local skilled workers, it is the unskilled local workers whose interests are threatened by optimal immigration policy.     

Price Changes and Some Underlying Aspects of Measurement of Poverty

The paper deals with effects of price changes on measurement of poverty. It is shown that there are situations, when prices and nominal incomes change, a higher nutritional intake or an increase in commodity consumption of the poor can be associated with higher poverty gaps and a higher poverty index of the society. A positive relationship of this kind is quite counter-intuitive in the context of poverty measurement. This is caused by the adjustment of the poverty line and/or incomes of one situation by the prices of the other for the purpose of comparison.

     

Uncertainty Associated with Future Environmental Costs and the Market's Differential Response to Earnings Information

This study examines whether the uncertainty arising from a firm's exposure to future environmental costs (environmental uncertainty) affects the market's price sensitivity to reported earnings. Specifically, when environmental uncertainty is significantly high, are investors more responsive to reported earnings released by 'high-polluting' firms than reported earnings announced by 'low-polluting' firms within the same industry? The initial impact of Title IV (the acid rain provisions) of the 1990 Clean Air Act Amendments (1990 CAAA) on the US electric utility industry provides the research setting required to isolate the effects of environmental uncertainty while addressing this question. Consistent with theoretical predictions, we find that the earnings response coefficients (ERCs) of high-polluting electric utilities are significantly greater than those of their low-polluting counterparts during a predicted period of elevated environmental uncertainty. In adjoining sample years associated with lower environmental uncertainty, we observe no statistical difference in the magnitude of the ERCs between these two groups. In addition, the study's findings suggest that the magnitude of the ERC is increasing in the firm's exposure to future environmental costs, after controlling for other factors that potentially affect ERCs.     

LIQUIDITY AND ASSET PRICING UNDER THE THREE‐MOMENT CAPM PARADIGM

We examine whether the use of the three‐moment capital asset pricing model can account for liquidity risk. We also make a comparative analysis of a four‐factor model based on Fama–French and Pástor–Stambaugh factors versus a model based solely on stock characteristics. Our findings suggest that neither of the models captures the liquidity premium nor do stock characteristics serve as proxies for liquidity. We also find that sensitivities of stock return to fluctuations in market liquidity do not subsume the effect of characteristic liquidity. Furthermore, our empirical findings are robust to differences in market microstructure or trading protocols between NYSE/AMEX and NASDAQ.     

The economic performance of the Russian economy in 2006 and a forecast for 2008–2010

This article examines the economic outcome of 2006 and builds a forecast for 2007–2010. The medium-term development risks of the Russian economy are analyzed.     

Using Medicare data for short-run projections of the elderly population.

As the elderly population of the United States grows in absolute number and as a proportion of total population, accurate projections of that population become increasingly important for sound policy decisions. Cohort component techniques are typically used for state and local projections of the elderly population, but are often outdated or even nonexistent for many local areas. This paper suggests an alternative approach, based on Medicare data and simple projection techniques. Projections for several base periods and projection horizons are made for all states and for counties in Florida and are compared with actual Medicare enrollment. On the basis of these comparisons it appears that Medicare data and simple projection techniques can produce very useful short-run projections of the elderly population for states and local areas.     

MANAGERIAL INCENTIVES AND CORPORATE DIVERSIFICATION STRATEGIES

Because the break-up of conglomerates typically produces substantial increases in shareholder wealth, many commentators have argued that the conglomerate form of organization is inefficient. This article reports the findings of a number of recent academic studies, including the authors' own, that examine the causes and consequences of corporate diversification. Although theoretical arguments suggest that corporate diversification can have benefits as well as costs, several studies have documented that diversified firms trade at a significant discount from their single-segment peers. Estimates of this discount range from 10–15% of firm value, and are larger for “unrelated” diversification than for “related” diversification. If corporate diversification has generally been a value-reducing managerial strategy, why do firms remain diversified? One possibility, which the authors label the “agency cost” hypothesis, is that top executives without substantial equity stakes may have incentives to maintain a diversification strategy even if doing so reduces shareholder wealth. But, as top managers' ownership stakes increase, they bear a greater fraction of the costs associated with value-reducing policies and are therefore less likely to take actions that reduce shareholder wealth. Also, to the extent that outside blockholders monitor managerial behavior, the agency cost hypothesis predicts that diversification will be less prevalent in firms with large outside blockholders. Consistent with this argument, the authors find that companies in which managers own a significant fraction of the firm's shares, and in which blockholders own a large fraction of shares, are significantly less likely to be diversified. If agency problems lead managers to maintain value-reducing diversification strategies, what is it that leads some of these same firms to refocus? The agency cost hypothesis predicts that managers will reduce diversification only if pressured to do so by internal or external mechanisms that reduce agency problems. Consistent with this argument, the authors find that decreases in diversification appear to be precipitated by market disciplinary forces such as block purchases, acquisition attempts, and management turnover.