Risk, ambiguity, and the exercise of employee stock options

Abstract

We investigate the importance of ambiguity, or Knightian uncertainty, in executives’ stock option exercise decisions. We develop an empirical estimate of ambiguity and include it in regression models alongside the traditional measure of risk, equity volatility. We show that each variable has a significant effect on the timing of option exercises, with volatility causing executives to hold options longer to preserve option value, and ambiguity increasing the tendency for executives to exercise early.