The contemporary structure of scientific activity, including the publication of papers in academic journals, citation behaviour, the clustering of research into specialties and so on has been intensively studied over the last fifty years. A number of quantitative relationships between aspects of the system have been observed. This paper reports on a simulation designed to see whether it is possible to reproduce the form of these observed relationships using a small number of simple assumptions. The simulation succeeds in generating a specialty structure with 'areas' of science displaying growth and decline. It also reproduces Lotka's Law concerning the distribution of citations among authors. The simulation suggests that it is possible to generate many of the quantitative features of the present structure of science and that one way of looking at scientific activity is as a system in which scientific papers generate further papers, with authors (scientists) playing a necessary but incidental role. The theoretical implications of these suggestions are briefly explored.

Central Statistics Office, various years.

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Departing from the observation that social security systems in different countries generate sharply different welfare outcomes, the question arises to what extent systems as such offer an explanation for better coverage of the poverty risk. In this article the micro-simulation technique is presented as an additional instrument in the field of comparative research. The micro-simulation technique offers the possibility of assessing the redistributive potential of different social security schemes, controlling for the socio-economic context. Institutional factors are thus separated from other factors which determine welfare outcomes. In this way a better understanding can be obtained of the redistributive criteria and mechanism operating within various systems. 1. Purpose In international comparative research, one important approach is the study of the effectiveness of social security systems and their impact on welfare outcomes in terms of poverty and income distribution of households. So far comparative empirical studies are primarily of a descriptive nature. [Deleeck,

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