Modeling Migration Careers,Using Data from a British Survey

Development of more sophisticated techniques for modeling longitudinal data has implications for improving our understanding of migration. This paper uses longitudinal data from the British Social Change and Economic Life initiative to disentangle the effects of population heterogeneity, progress through the life cycle and secular change on observed migration differentials. The data consist of retrospective life histories from people sampled in several contrasting localities in Great Britain, in which residential moves can be linked to changes in occupation and household structure. We present a framework for analysis of data of this type using a generalized linear modeling approach, together with results concerning variations in the probability of migration with age, gender, and changes in household and occupational circumstances. Of particular note is the evidence of substantial duration-of-residence effects and an unexpected later-career increase in migration propensity.     

Impacts of Multiple-Period Lags in Dynamic Logit Models

This paper will provide an introduction to a new field of research, viz. the sensitivity of the solution trajectory of a dynamic logit model (belonging to the class of discrete choice models) in the light of a multiperiod lag structure. It is well known from recent advances in the area of chaos and turbulence theory that the stability of a dynamic system is critically dependent on various factors, such as threshold values of parameters, initial conditions, and also the lag structure. This paper aims to identify the consequences of different lag structures in dynamic logit models (including also dynamic spatial interaction models). Various simulation experiments will be used to show that the onset of instability of the solution trajectory tends to decrease as the number of time lags increases (depending also on the growth rate of the system).     

The history of the neurological examination. Part 1: ancient and pre-modern history--3000 BC to AD 1850

Every time a physician conducts a neurological examination the process continues a biomedical search for understanding the nervous system which is as ancient as the earliest civilizations in human history. Most of the modern neurological examination evolved in a short time span, between 1850 and 1914, but the origins of neurology as a medical quest for knowledge date to the first evolution of urban life, in the valleys of the Euphrates and the Nile. This paper reviews this history in two chronological segments: part 1 up to 1850 and part 2 the subsequent period.