Data on the spread of invasive weeds into arid western lands are used to evaluate the environmental and economic importance of controlling invasive weed infestations early. Variable rate and constant rate infestation expansion paths are estimated. The implications of variable vs. constant infestation growth rates for projecting both biophysical and economic effects are illustrated. The projections derived from both constant and variable growth rate expansion paths support the contention that it is expedient to control new infestations early.

Restrictions on the ownership of farmland by nonresidents of Saskatchewan were imposed by the Farmland Security Act (FSA) in 1974. The FSA has been blamed by some observers for depressed provincial land values. An adaptive expectations present value model is developed to estimate the effects of the FSA, with the province of Alberta included as a control. Results of seemingly unrelated regressions and generalized autoregressive conditional heteroscedasticity estimates find no statistically significant effect of the FSA on the value of land in Saskatchewan. This may indicate that the effect of the regulatory change is too small to be measured accurately.

This lesson describes how a government decides whether and how much it should spend on vulnerability reduction. There are techniques and methods by which decision-makers compare development alternatives. The differences between the risk that a potentially catastrophic event will occur and uncertainty are described, with uncertainty providing greater difficulty in economic analyses. There is a range of methods for identifying the complex mix of competing costs and benefits associated with any restructuring of investment priorities to accomplish disaster mitigation. The possibilities are described in terms of the opportunity costs and present value. Impact and consequent losses include: (1) direct monetary effects; (2) indirect monetary effects; (3) direct, non-monetary effects; (4) indirect, non-monetary effects; and (5) loss of non-renewable natural resources. The difficulties in assigning values to these effects are described, as well as the means of judging the costeffectiveness of such interventions. An advantage of screening projects using a framework of analytical methods is that it can assist in focusing on a variety of possible outcomes and make the factors influencing these outcomes quite explicit.

We study the present value Z∞ = ∫0∞ e-Xt-dYt where (X,Y) is an integrable Lévy process. This random variable appears in various applications, and several examples are known where the distribution of Z∞ is calculated explicitly. Here sufficient conditions for Z∞ to exist are given, and the possibility of finding the distribution of Z∞ by Markov chain Monte Carlo simulation is investigated in detail. Then the same ideas are applied to the present value Z-∞ = ∫0∞ exp{-∫0tRsds}dYt where Y is an integrable Lévy process and R is an ergodic strong Markov process. Numerical examples are given in both cases to show the efficiency of the Monte Carlo methods.