  According to conventional wisdom, ambiguity accelerates optimal timing by
decreasing the value of waiting in comparison with the unambiguous benchmark
case. We study this mechanism in a multidimensional setting and show that in a
multifactor model ambiguity does not only influence the rate at which the
underlying processes are expected to grow, it also affects the rate at which
the problem is discounted. This mechanism where nature also selects the rate at
which the problem is discounted cannot appear in a one-dimensional setting and
as such we identify an indirect way of how ambiguity affects optimal timing.
