Flows of constant mean curvature tori in the 3-sphere: The equivariant case

We present a deformation for constant mean curvature tori in the 3-sphere. We show that the moduli space of equivariant constant mean curvature tori in the 3-sphere is connected, and we classify the minimal, the embedded, and the Alexandrov embedded tori therein. We conclude with an instability result.Comment: v2: 33 pages, 9 figures. Instability result adde

Only in the Heat of the Moment? A Study of the Relationship between Weather and Mortality in Germany

In this study we analyze the relationship between heat events and mortality in Germany. The main research questions are: Does heat lead to rising mortality and if yes, are the effects persistent or compensated for in the near future? Furthermore, we consider differences between heat effects in urban and rural environments. Cause specific daily mortality and meteorological data is connected on the county level. We allow for static as well as dynamic relations between extreme temperatures and mortality and implement several panel data estimation approaches. We find that heat has a significant positive impact on mortality. The strongest effects can be measured on the day when heat occurs and the first week afterwards. The mortality increase ranges between 0.003 and 3.5 per 100,000 inhabitants depending on the particular death cause. We do not find a significant negative, and thus compensating impact in a medium term, which is in the contrary to the Harvesting Hypothesis. Using a value of statistical life approach we estimate that one additional hot day in Germany induces for the overall population a loss of m € 1,861. Moreover, the environment plays an important role. The heat induced increase in mortality is significantly higher in urban areas.Climate Change, Harvesting Hypothesis, Heat Waves, Mortality, Urban Heat Island effect

Optimal Fiscal and Monetary Policy Under Sticky Prices

This paper studies optimal .scal and monetary policy under sticky product prices. The theoretical framework is a stochastic production economy without capital. The government finances an exogenous stream of purchases by levying distortionary income taxes, printing money, and issuing one-period nominally risk-free bonds. The main findings of the paper are: First, for a miniscule degree of price stickiness (i.e., many times below available empirical estimates)the optimal volatility of in.ation is near zero. This result stands in stark contrast with the high volatility of inflation implied by the Ramsey allocation when prices are flexible. The finding is in line with a recent body of work on optimal monetary policy under nominal rigidities that ignores the role of optimal fiscal policy. Second, even small deviations from full price flexibility induce near random walk behavior in government debt and tax rates, as in economies with real non-state-contingent debt only. Finally, sluggish price adjustment raises the average nominal interest rate above the one called for by the Friedman rule.

Optimal Fiscal and Monetary Policy Under Imperfect Competition

This paper studies optimal fiscal and monetary policy under imperfect competition in a stochastic, flexible-price, production economy without capital. It shows analytically that in this economy the nominal interest rate acts as an indirect tax on monopoly profits. Unless the social planner has access to a direct 100 percent tax on profits, he will always find it optimal to deviate from the Friedman rule by setting a positive and time-varying nominal interest rate. The dynamic properties of the Ramsey allocation are characterized numerically. As in the perfectly competitive case, the labor income tax is remarkably smooth, whereas inflation is highly volatile and serially uncorrelated. An exact numerical solution method to the Ramsey conditions is proposed.

Anticipated Ramsey Reforms and the Uniform Taxation Principle: the Role of International Financial Markets

This paper studies the role of asset-market completeness for the properties of optimal policy. A suitable framework for this purpose is the small open economy with complete international asset markets. For in this environment changes in policy represent country-specific risk diversifiable in world markets. Our main finding is that the fundamental public finance principle whereby when taxes on all final goods are available, it is optimal to tax final goods uniformly fails to obtain. In general, uniform taxation is optimal because it amounts to a nondistorting tax on fixed factors of production. In the open economy this principle fails because when households can insure against the risk of a policy reform, initial private asset holdings are contingent on actual policy and thus no longer represent an inelastically supplied source of income. Two further differences between optimal policy in the closed and open economies with complete markets are: (a) In the open economy, optimal consumption and income tax rates are unchanged in response to government purchases shocks. By contrast, in the closed economy tax rates do respond to innovations in public spending. (b) In the open economy, the Friedman rule is optimal only if the Ramsey planner has access to consumption taxes. In the absence of consumption taxes, deviations from the Friedman rule are large. On the other hand, in the closed economy, the availability of either consumption or income taxes suffices to render the Friedman rule optimal.

Optimal Inflation Stabilization in a Medium-Scale Macroeconomic Model

This paper characterizes Ramsey-optimal monetary policy in a medium-scale macroeconomic model that has been estimated to fit well postwar U.S.\ business cycles. We find that mild deflation is Ramsey optimal in the long run. However, the optimal inflation rate appears to be highly sensitive to the assumed degree of price stickiness. Within the window of available estimates of price stickiness (between 2 and 5 quarters) the optimal rate of inflation ranges from -4.2 percent per year (close to the Friedman rule) to -0.4 percent per year (close to price stability). This sensitivity disappears when one assumes that lump-sum taxes are unavailable and fiscal instruments take the form of distortionary income taxes. In this case, mild deflation emerges as a robust Ramsey prediction. In light of the finding that the Ramsey-optimal inflation rate is negative, it is puzzling that most inflation-targeting countries pursue positive inflation goals. We show that the zero bound on the nominal interest rate, which is often cited as a rationale for setting positive inflation targets, is of no quantitative relevance in the present model. Finally, the paper characterizes operational interest-rate feedback rules that best implement Ramsey-optimal stabilization policy. We find that the optimal interest-rate rule is active in price and wage inflation, mute in output growth, and moderately inertial. This rule achieves virtually the same level of welfare as the Ramsey optimal policy.

Optimal Simple and Implementable Monetary and Fiscal Rules

The goal of this paper is to compute optimal monetary and fiscal policy rules in a real business cycle model augmented with sticky prices, a demand for money, taxation, and stochastic government consumption. We consider simple policy rules whereby the nominal interest rate is set as a function of output and inflation, and taxes are set as a function of total government liabilities. We require policy to be implementable in the sense that it guarantees uniqueness of equilibrium. We do away with a number of empirically unrealistic assumptions typically maintained in the related literature that are used to justify the computation of welfare using linear methods. Instead, we implement a second-order accurate solution to the model. Our main findings are: First, the size of the inflation coefficient in the interest-rate rule plays a minor role for welfare. It matters only insofar as it affects the determinacy of equilibrium. Second, optimal monetary policy features a muted response to output. More importantly, interest rate rules that feature a positive response of the nominal interest rate to output can lead to significant welfare losses. Third, the optimal fiscal policy is passive. However, the welfare losses associated with the adoption of an active fiscal stance are negligible.

Optimal Fiscal and Monetary Policy in a Medium-Scale Macroeconomic Model: Expanded Version

In this paper, we study Ramsey-optimal fiscal and monetary policy in a medium-scale model of the U.S.\ business cycle. The model features a rich array of real and nominal rigidities that have been identified in the recent empirical literature as salient in explaining observed aggregate fluctuations. The main result of the paper is that price stability appears to be a central goal of optimal monetary policy. The optimal rate of inflation under an income tax regime is half a percent per year with a volatility of 1.1 percent. This result is surprising given that the model features a number of frictions that in isolation would call for a volatile rate of inflation---particularly nonstate-contingent nominal public debt, no lump-sum taxes, and sticky wages. Under an income-tax regime, the optimal income tax rate is quite stable, with a mean of 30 percent and a standard deviation of 1.1 percent. Simple monetary and fiscal rules are shown to implement a competitive equilibrium that mimics well the one induced by the Ramsey policy. When the fiscal authority is allowed to tax capital and labor income at different rates, optimal fiscal policy is characterized by a large and volatile subsidy on capital.

Solving Dynamic General Equilibrium Models Using a Second-Order Approximation to the Policy Function

This paper derives a second-order approximation to the solution of a general class of discrete- time rational expectations models. The main theoretical contribution of the paper is to show that for any model belonging to the general class considered, the coefficients on the terms linear and quadratic in the state vector in a second-order expansion of the decision rule are independent of the volatility of the exogenous shocks. In other words, these coefficients must be the same in the stochastic and the deterministic versions of the model. Thus, up to second order, the presence of uncertainty affects only the constant term of the decision rules. In addition, the paper presents a set of MATLAB programs designed to compute the coefficients of the second-order approximation. The validity and applicability of the proposed method is illustrated by solving the dynamics of a number of model economies.