We develop a model of GDP growth under which regime changes are triggered stochastically by an observable tension index , constructed as the geometric sum of deviations of actual GDP growth from a corresponding sustainable rate. Within expansionary regimes, the tension index tends to increase, which heightens the probability of a regime change. Given a regime change, the process becomes reversed, and the tension index begins to decline along a newly established path. Linking the behavior of the tension index to GDP growth enables us to capture floor and ceiling effects.

Super-experienced bidders have learned to overcome the winner's curse but still earn less than 50% of Nash equilibrium profits. Subjects deviate from the complicated Nash strategy, employing piecewise-linear bid functions that are capable, in principle, of generating an equilibrium with average profits at or above the Nash benchmark. Thus, limited computational abilities alone cannot account for the reduced earnings. Further, subjects are far from best responding within this family of piecewise-linear bid functions. Alternative factors contributing to these reduced earnings are explored.