A New Test for Rational Speculative Bubbles using Forward Exchange Rates: The Case of the Interwar German Hyperinflation

The probabilistic structure of periodically collapsing bubbles implies different values for the slope coefficient of alternative efficient market hypothesis tests depending on whether the bubble is in an explosive regime or not. We exploit this fact and propose a new method for bubble detection.<br/>The method does not require the specification of the process followed by fundamentals, it is not affected by a possible explosive root of the determinants<br/>of the asset price, and provides a date-stamping strategy. We analyze the Reichsmark/Dollar exchange rate for the interwar German hyperinflation period and identify periods of rational exuberance.