A Recursive Income Model for Canadians : The Direct and Indirect Effects of Family Background (Working Paper 28)

This paper presents the results of a multi-equation income model which has been estimated for Canadian men and women which incorporates the effects of a number of important family background variables, including mother’s and father’s education, parents’ immigration status, their age at immigration, place of birth, language development, and learning background. Not only education, but also the individual’s tested literacy and numeracy levels are treated as intermediate outcomes which are affected by background and which, in turn, affect income. Many of the background variables are found to have important indirect effects on income which would be missed by more conventional approaches. We also find some interesting gender aspects with respect to the influences of parents’ educations on their children’s outcomes. Various policy implications of the findings are discussed.

An impulsive differential equation model for Marek's disease

Many dynamical processes are subject to abrupt changes in state. Often these perturbations can be periodic and of short duration relative to the evolving process. These types of phenomena are described well by what are referred to as impulsive differential equations, systems of differential equations coupled with discrete mappings in state space. In this thesis we employ impulsive differential equations to model disease transmission within an industrial livestock barn. In particular we focus on the poultry industry and a viral disease of poultry called Marek's disease. This system lends itself well to impulsive differential equations. Entire cohorts of poultry are introduced and removed from a barn concurrently. Additionally, Marek's disease is transmitted indirectly and the viral particles can survive outside the host for weeks. Therefore, depopulating, cleaning, and restocking of the barn are integral factors in modelling disease transmission and can be completely captured by the impulsive component of the model. Our model allows us to investigate how modern broiler farm practices can make disease elimination difficult or impossible to achieve. It also enables us to investigate factors that may contribute to virulence evolution. Our model suggests that by decrease the cohort duration or by decreasing the flock density, Marek's disease can be eliminated from a barn with no increase in cleaning effort. Unfortunately our model also suggests that these practices will lead to disease evolution towards greater virulence. Additionally, our model suggests that if intensive cleaning between cohorts does not rid the barn of disease, it may drive evolution and cause the disease to become more virulent.