Robust risk choice under high-water mark contract

By assuming that a risk-neutral hedge fund manager has ambiguous beliefs about the return process of risky asset, we study his robust risk choice under the high-water mark. The results show that without management fees, ambiguity aversion induces the manager to take more risk as the fund is close to the termination but take less risk as the fund approaches the high-water mark. With management fees, ambiguity aversion increases the induced risk aversion and moderates the manager’s incentive to take risk, predicting that it is the manager with higher rates of management fees that reduces the risky asset holdings more when he becomes less confident and/or more pessimistic about the future returns. The model implies that managers’ ambiguity aversion is a possible factor explaining hedge fund activities in stock markets during the financial crisis of 2007–2009 and in US Treasury markets during COVID-19 crisis. Finally, taxation is taken into account.