This paper studies the optimal reinsurance-investment problems for an insurance company where the claim process follows a Brownian motion with drift. It turns out that there is a region where the probability of drawdown, namely, the probability that the value of the insurer's surplus process reaches some fixed fractional value of its maximum value to date is positive. Then in the complementary region, drawdown can be avoided with certainty. For this reason, we call the former region the "danger-zone" and "safe-region" for the latter. In the danger-zone, we consider the problem of minimizing the probability of drawdown; and in the safe-region, we turn our attention to the optimization problem of minimizing the expected time to reach a given capital level. Using the technique of stochastic control theory and the corresponding Hamilton-Jacobi-Bellman equation, explicit expressions of the optimal reinsurance-investment strategies and the associated value functions are derived for the two optimization problems. Moreover, we provide several detailed comparisons to investigate the impact of some important parameters on the optimal strategies and illustrate the observation from behavior finance of view.
K E Y W O R D Sdiffusion approximation model, Hamilton-Jacobi-Bellman equation, investment, proportional reinsurance, stochastic optimal control