Optimal Taxation with Endogenous Insurance Markets

We study optimal tax policy in a dynamic private information economy with endogenous private markets. We characterize efficient allocations and competitive equilibria. A standard assumption in the literature is that trades are observable by all agents. We show that in such an environment the competitive equilibrium is efficient. The only effect of government interventions is crowding out of private insurance. We then relax the assumption of observability of consumption and consider an environment with unobservable trades in competitive markets. We show that efficient allocations have the property that the marginal product of capital is different from the market interest rate associated with unobservable trades. In any competitive equilibrium without taxation, the marginal product of capital and the market interest rate are equated, so that competitive equilibria are not efficient. Taxation of capital income can be welfare-improving because such taxation introduces a wedge between market interest rates and the marginal product of capital and allows agents to obtain better insurance in private markets. Finally, we use plausibly calibrated numerical examples to compute optimal taxes and welfare gains and compare results to an economy with a restricted set of tax instruments, and to an economy with observable trades.

Modeling style rotation: switching and re-switching

The purpose of this paper is to investigate the dynamics and statistics of style rotation based on the Barberis-Shleifer model of style switching. Investors in stocks regard the forecasting of style-relative performance, especially style rotation, as highly desirable but difficult to achieve in practice. Whilst we do not claim to be able to do this in an empirical sense, we do provide a framework for addressing these issues. We develop some new results from the Barberis-Shleifer model which allows us to understand some of the time series properties of style relative price performance and determine the statistical properties of the time until a switch between styles. We apply our results to a set of empirical data to get estimates of some of the model parameters including the level of risk aversion of market participants

Designing Optimal Disability Insurance: A Case for Asset Testing

The paper analyzes an implementation of an optimal disability insurance system as a competitive equilibrium with taxes. The problem is modeled as a dynamic mechanism design problem in which disability is unobservable. We show that an asset-tested disability system in which a disability transfer is paid only if an agent has assets below a specified maximum implements the optimum. The logic behind the result is as follows: we show that an agent who falsely claims disability has higher savings than a truly disabled agent, and an asset test prevents false claimants from receiving disability. We also evaluate welfare benefits of asset testing. For a calibrated economy, we numerically compare the optimal system to the best system without asset testing. We find that gains of asset testing are significant and equal to about 0.65% of consumption.