  How do decisions change with the economic environment and with time? This
paper studies general nonstationary stopping problems and provides the
methodological tools to answer these questions. First, we identify conditions
that ensure a monotone relation between decisions' timing and outcomes. These
conditions apply to a prevalent class of economic environments. Second, we
develop a theory of monotone comparative statics for stopping problems,
offering general and unifying qualitative insights into the decision-maker's
value and stopping behavior. We apply our results to models of information
acquisition, bankruptcy, irreversible investment, and option pricing to explain
documented patterns at odds with current theories.
