Search

Hester SM, Brooks SJ, Cacho OJ & Panetta FD (2010). Applying a simulation model to the management of an infestation of Miconia calvescens in the wet tropics of Australia. Weed Research 50, 269–279. A simulation model that combines biological, search and economic components is applied to the eradication of a Miconia calvescens infestation at El Arish in tropical Queensland, Australia. Information on the year M. calvescens was introduced to the site, the number of plants controlled and the timing of control, is used to show that currently there could be M. calvescens plants remaining undetected at the site, including some mature plants. Modelling results indicate that the eradication programme has had a significant impact on the population of M. calvescens, as shown by simulated results for uncontrolled and controlled populations. The model was also used to investigate the effect of changing search effort on the cost of and time to eradication. Control costs were found to be negligible over all levels of search effort tested. Importantly, results suggest eradication may be achieved within several decades, if resources are increased slightly from their current levels and if there is a long-term commitment to funding the eradication programme. [ABSTRACT FROM AUTHOR]

Search theory is the conventional framework used for analyzing the factors influencing unemployment. But the empirical implementation of the theory poses major challenges since many of the variables of conceptual interest are not observed in the data. The goals of this paper are to test a prediction of search theory which is possible given the available data on Australian native and immigrant unemployment experience, and to examine the operational weaknesses inherent in the theory when proxy variables must be used to capture unobserved parameters of the model.
Two major points follow from the analysis, neither of which has found its way to the forefront of policy or method. First, participants in the debate on the economic assimilation of immigrants (Borjas, 1985; Chiswick, 1978) miss the very important point that conclusions concerning the relative labour market success of immigrants differ considerably depending on the measurable skill levels of groups. Second, the usefulness of search theory in providing testable hypotheses is demonstrated to be so limited as to constitute a credible case against its general application.
Section II describes the theoretical model and explains its scope for formulating direct tests of particular hypotheses. In Section III possible empirical estimation of unemployment determinants is examined, there being apparently (only) one unambiguous relationship that is predicted from the theory. This is that, ceteris paribus, low skill (schooled) immigrants are less likely to be unemployed than like natives, an hypothesis supported by the empirical results reported in Section IV in which immigrant and native unemployment determinants are examined. It is concluded, in Section V, that whereas empirical constraints frequently inhibit useful applications of search theory, in this (unusual) instance a (policy relevant) insight related to immigrant unemployment has been forthcoming. [ABSTRACT FROM AUTHOR]