Seasonal fertility cycles in rural Egypt: Behavioral and biological linkages

The annual birth cycle in rural Egypt peaks in December and has two distinguishable minima in June and September. This pattern bears a striking inverse resemblance to the seasonal movements of employment and wages. Infant and child mortality and marriage also display stable, though different seasonal patterns. The paper explores whether the correlation between labor demand, mortality events and fertility reflect some causal behavioral relationship. It is shown that the probability of a birth is lower in months with high opportunity cost of time. Direct replacement is a significant phenomenon in rural Egypt and it occurs fairly quickly.     

A Simple Approach to Fitting Bayesian Survival Models

There has been much recent work on Bayesian approaches to survival analysis, incorporating features such as flexible baseline hazards, time-dependent covariate effects, and random effects. Some of the proposed methods are quite complicated to implement, and we argue that as good or better results can be obtained via simpler methods. In particular, the normal approximation to the log-gamma distribution yields easy and efficient computational methods in the face of simple multivariate normal priors for baseline log-hazards and time-dependent covariate effects. While the basic method applies to piecewise-constant hazards and covariate effects, it is easy to apply importance sampling to consider smoother functions.     

The cylindrical structure of political involvement

This research is devoted to a methodological study of interrelations among varieties of involvement in political issues, utilizing data designed and gathered in the context of the Israel election campaign for the Seventh Knesset in 1969. The observations on political involvement were defined by means of a mapping sentence. The interrelations were studied by calculating a weak monotonicity coefficient between each pair of variables. This correlation matrix was submitted to a smallest space analysis (SSA-I) in order to help ascertain the correspondence between the structure of the matrix and the facets of political issues in the mapping sentence. It is hypothesized that the regression of one form of involvement on another should be monotone and of positive sign. Such a ‘first law’ of involvement does hold empirically here. Furthermore, the structure of the intercorrelation matrix can be represented geometrically by a cylindrical interpretation of the SSA space which corresponds to the facet design of the varieties of involvement. The axis of the cylinder distinguishes between instrumental and cognitive involvement, while the circularity within strata of the cylinder corresponds to the facet of political issues which are the objects of the involvement.     

Arrow-Pratt Risk Aversion, Risk Premium and Decision Weights

This paper analyzes two issues: (a) the effect of decision-weights on risk premium, and (b) whether risk-aversion characterizes most investors. We theoretically show that cumulative prospect theory decision-weights systematically increase Arrow's risk premium, and may induce a positive risk premium even in the absence of risk-aversion. However, decision-weights may either increase or reduce Pratt's risk premium. We present three experiments revealing a striking result: a large proportion of the subjects' choices contradicts risk-aversion. This may be due to non-concave preferences, or to decision-weights. This result may have a dramatic impact on equilibrium models in economics and finance.     

Diversity Training and Intergroup Contact: A Call to Action Research

Diversity training is a type of prejudice reduction and social inclusion intervention in need of "action research"—an integration of research and theory with practice ( Lewin, 1946 ). Hundreds of workplaces and schools use some form of diversity training, but most interventions are not grounded in theory and there is little evidence of program impact. A recent study of a school diversity training program illustrates how action research can address theoretical issues using experimental methods and unobtrusive outcome measures. For future research, the literature on intergroup contact ( Pettigrew, 1998 ) can provide theoretical guidance while testing and refining its principles in the application and investigation of diversity training. Action research will benefit diversity training and the broader theoretical and applied project of prejudice reduction and the promotion of social inclusion.