Fear of model misspecification and the robustness premium

Robust decision making implies welfare costs or robustness premia when the approximating model is the true data generating process. To examine the importance of these premia at the aggregate level we employ a simple two-sector dynamic general equilibrium model with human capital and introduce an additional form of precautionary be- havior. The latter arises from the robust decision maker's ability to reduce the effects of model misspecification through allocating time and existing human capital to this end. We find that the extent of the robustness premia critically depends on the productivity of time rela- tive to that of human capital. When the relative efficiency of time is low, despite transitory welfare costs, there are gains from following ro- bust policies in the long-run. In contrast, high relative productivity of time implies misallocation costs that remain even in the long-run. Fi- nally, depending on the technology used to reduce model uncertainty, we find that while increasing the fear of model misspecification leads to a net increase in precautionary behavior, investment and output can fall.

An Introduction to Recursive Partitioning: Rationale, Application and Characteristics of Classification and Regression Trees, Bagging and Random Forests

Recursive partitioning methods have become popular and widely used tools for nonparametric regression and classification in many scientific fields. Especially random forests, that can deal with large numbers of predictor variables even in the presence of complex interactions, have been applied successfully in genetics, clinical medicine and bioinformatics within the past few years. High dimensional problems are common not only in genetics, but also in some areas of psychological research, where only few subjects can be measured due to time or cost constraints, yet a large amount of data is generated for each subject. Random forests have been shown to achieve a high prediction accuracy in such applications, and provide descriptive variable importance measures reflecting the impact of each variable in both main effects and interactions. The aim of this work is to introduce the principles of the standard recursive partitioning methods as well as recent methodological improvements, to illustrate their usage for low and high dimensional data exploration, but also to point out limitations of the methods and potential pitfalls in their practical application. Application of the methods is illustrated using freely available implementations in the R system for statistical computing

Human capital accumulation and transition to skilled employment

This paper assesses the impact of investment- and education-specific technical change on occupational transition and the skill premium in a model with human capital. In this framework, human capital augments labor productivity and also facilitates the transition to skilled employment. In line with empirical evidence, this setup predicts that an increase in the productivity of physical capital (investment-specific change) leads to very small increases in the relative supply of skilled workers and to significant and rising increases in the skill premium. Additionally, reforms that improve the productivity of resources used in education (education-specific change) reduce wage inequality and increase mobility

Optimal taxation and the skill premium

The stylized facts suggest a negative relationship between tax progres- sivity and the skill premium from the early 1960s until the early 1990s, and a positive one thereafter. They also generally imply rising tax progressivity, except for the 1980s. In this paper, we ask whether optimal tax policy is consistent with these observations, taking into account the demographic and technological factors that have also affected the skill premium. To this end, we construct a dynamic general equilibrium model in which the skill premium and the progressivity of the tax system are endogenously determined, with the latter being optimally chosen by a benevolent government. We find that optimal policy delivers both a progressive tax system and model predictions which are generally consistent, except for the 1980s, with the stylized facts relating to the skill premium and progressivity. To capture the patterns in the data over the 1980s requires that we adopt a government policy which is biased towards the interests of skilled agents. Thus, in addition to demo- graphic and technological factors, changes in the preferences of policy-makers appear to be a potentially important factor in determining the evolution of the observed skill premium.skill premium, optimal tax policy, government preferences

Time-consistent fiscal policy under heterogeneity: Conflicting or common interests?

This paper studies the aggregate and distributional implications of Markov-perfect tax-spending policy in a neoclassical growth model with capitalists and workers. Focusing on the long run, our main …ndings are: (i) it is optimal for a benevolent government, which cares equally about its citizens, to tax capital heavily and to subsidise labour; (ii) a Pareto improving means to reduce inefficiently high cap- ital taxation under discretion is for the government to place greater weight on the welfare of capitalists; (iii) capitalists and workers inter- ests, regarding the optimal amount of "capitalist bias", are not aligned implying a trade-off between efficiency and equity.Optimal fiscal policy, Markov-perfect equilibrium, heterogenous agents

The distributional consequences of supply-side reforms in general equilibrium

This paper addresses the issue on whether tax reforms consistent with lower public debt-to-GDP in the long-run can lead to a more efficient and equitable economy. To this end we solve a heterogeneous agent model comprised of a government, a representative capitalist and representative skilled and unskilled workers, under both rational expectations and adaptive learning. Our main findings are that (i) reductions in capital taxation, while beneficial at the aggregate level, lead to increased inequality mainly due to the substitutability of un- skilled labour and capital; (ii) a fall in taxation for skilled labour is Pareto improving, which is largely explained by its complementarity with the other factor inputs; (iii) all agents would prefer increasing the tax rate on capital to increasing the tax rate on skilled and un- skilled labour since it leads to relatively lower welfare losses; and (iv) heterogeneity in initial beliefs under adaptive learning quantitatively matters for welfare.tax reform, structural heterogeneity, inequality, adaptive learning

The macroeconomic impacts of foreign direct investment: the Scottish case

A two sector multi-equation macro-econometric model of Scottish manufacturing industry was constructed and distinctive characteristics of the home and foreign sectors explored. In addition dynamic simulations were carried out to elucidate the policy implications of alternative scenarios