Complex solutions of nonconcave dynamic optimization models

Summary In this paper we consider a class of time discrete intertemporal optimization models in one dimension. We present a technique to construct intertemporal optimization models with nonconcave objective functions, such that the optimal policy function coincides with any pre-specifiedC ² function. Our result is a variant of the approach presented in a seminal paper by Boldrin and Montrucchio (1986). Whereas they solved the inverse problem for the reduced form models, we address the different question of how to construct both reduced and primitive form models. Using our technique one can guarantee required qualitative properties not only in reduced, but also in primitive form. The fact that our constructed model has a single valued and continuous optimal policy is very important as, in general, nonconcave problems yield set valued optimal policy correspondences which are typically hard to analyze. To illustrate our constructive approach we apply it to a simple nonconcave model.We are grateful for the helpful comments of L. Montrucchio, K. Nishimura, T. Mitra and an anonymous referee. Financial support of the Austrian Science Foundation under contract No. P7783-PHY and No. J01003-SOZ is gratefully acknowledged. This paper was written while M. Kopel was visiting the Department of Economics, Cornell University.     

Dynamic R&D competition with memory

We consider a differential game of R&D competition and explore the impact of rivalry on the firms' investment behavior over time. Using closed-loop strategies and hence allowing for strategic interactions among rival firms we show that R&D spending by the individual competitor is increased due to competition in the race for priority. This leads us to argue that competitive encounters enhance R&D activities at the same time as increasing efficiency in the race for a technological breakthrough.     

Nach der Wahl: Was sind die wichtigsten wirtschaftspolitischen Herausforderungen?

Even though Germany’s economy is currently going strong, the country still faces enormous challenges if it wants to maintain and increase this prosperity. The new government should take this opportunity to set the course for the future by encouraging the digitalisation of the economy and the society as well as by ensuring that the ongoing energy transition is sustainable and efficient. Other challenges include the adverse effects of globalisation on parts of society and the uneven distribution of income and wealth. But the actual magnitude of the government’s room to manoeuver is up for debate. The new government’s fiscal space might be more limited than it seems, since an automatic adjustment of the income tax to inflation and growth is required to end the bracket creep. Given that transfer programmes are being phased out, the federal income tax surcharge to finance German unification also needs to be abolished. Further budget pressure stems from the pension system and from demands by state and local as well as European governments. The new German government should use the next governing period to initiate fundamental reforms of economic and fiscal policy that will provide adequate answers to long-run challenges.     

Energy balance climate models and general equilibrium optimal mitigation policies

In a general equilibrium model of the world economy, we develop a two-dimensional energy balance climate model featuring heat diffusion and anthropogenic forcing driven by global fossil fuel use across the sphere of the Earth. This introduces an endogenous location dependent temperature function, driving spatial characteristics, in terms of location dependent damages resulting from local temperature anomalies into the standard climate-economy framework. We solve the social planner's problem and characterize the competitive equilibrium for two polar cases differentiated by the degree of market integration. We define optimal taxes on fossil fuel use and how they may implement the planning solution. Our results suggest that if the implementation of international transfers across latitudes is not possible then optimal taxes are in general spatially non-homogeneous and may be lower at poorer latitudes. The degree of spatial differentiation of optimal taxes depends on heat transportation. By employing the properties of the spatial model, we show by numerical simulations how the impact of thermal transport across latitudes on welfare can be studied.     

The accomplishment of the Maastricht criteria with respect to initial debt

The reduction of government debt to 60% of the GDP in order to satisfy the requirements of the Maastricht Treaty for participation in the European Monetary Union is one of the primary economic-policy goals for most of the European Union countries. The first aim of the present paper is to characterize the optimal path of the primary surplus that leads to the achievement of this Maastricht target. Using optimal-control theory we are able to determine an upper bound of the public-debt-to-GDP ratio above which no retrenchment policy becomes effective. The second issue taken up is that of the sensitivity analysis with respect to the initial level of the debt-to-GDP ratio, the growth rate of the economy, the interest rate, the inflation rate, and the inverse of the velocity of the monetary base circulation.     

A Proposal for the Efficient Taxation of All Business Income in the EU

There is a growing awareness in many EU member states that business taxation solely on the basis of “taxable profits” enables, in particular, multinational companies to avoid paying taxes, with negative consequences both for tax revenue and—in the longer run—also for the stability of the economy. The following article proposes the taxation of all compensation of capital—not only profit for equity, but also interest for outside capital and licence fees for outside rights—at the site of production.     

Country size and the rule of law: Resuscitating Montesquieu

In this paper, we demonstrate that there is a robust negative relationship between the size of country territory and a measure of the rule of law for a large cross-section of countries. We outline a framework featuring two main reasons for this regularity; firstly that institutional quality often has the character of a local public good that is imperfectly spread across space from the core of the country to the hinterland, and secondly that a large territory usually is accompanied by valuable rents and a lack of openness that both tend to distort property rights institutions. Our empirical analysis further shows some evidence that whether the capital is centrally or peripherally located within the country matters for the average level of rule of law.