We present a conceptual, but empirically applicable, model for determining the optimal allocation of resources between exclusion and control activities for managing an invasive species with an uncertain discovery time. This model is used to investigate how to allocate limited resources between activities before and after the first discovery of an invasive species and the effects of the characteristics of an invasive species on limited resource allocation. The optimality conditions show that it is economically efficient to spend a larger share of outlays for exclusion activities before, rather than after, a species is first discovered, up to a threshold point. We also find that, after discovery, more exclusionary measures and fewer control measures are optimal, when the pest population is less than a threshold. As the pest population increases beyond this threshold, the exclusionary measures are no longer optimal. Finally, a comparative dynamic analysis indicates that the efficient level of total expenditures on preventive and control measures decreases with the level of the invasive species stock and increases with the intrinsic population growth rate, the rate of additional discoveries avoided, and the maximum possible pest population.

The literature developed by scholars dealing with policy agendas suggests that it is more important to look at changes in governments’ priorities rather than in their ideology, and criticizes the partisan theory as inadequate. However, hypotheses based on conventional wisdom and normative theories, holding that the identity of the governing parties matters for the allocation of public expenditures, are still recurrent in the debate. And many empirical studies found mixed evidence on the importance of party ideology. Focussing on Italy (1948–2009), this article empirically tests whether shifts in governments’ ideology and policy priorities are related to public spending changes in four policy sectors. The results indicate that shifts in governments’ priorities are related with public spending changes in welfare and defence, while they are not relevant to explain changes in public order and education spending. Government ideology is relevant only when it comes to defence spending, but this influence can be hindered by veto players. We argue that these findings do not disprove the importance of partisan politics but warn us against relying too much on the distinction between left and right parties. At the same time, more research is needed to understand under which conditions partisan preferences translate into changing public policies.