Do bubbles occur in the gold price? An investigation of gold lease rates and Markov Switching models

ADF and cointegration tests point to a rational speculative bubble. The more theoretically valid Markov Switching ADF test gives mixed evidence. No bubble is found to be present if we allow the variance to switch between regimes, the gold and its lease rate relationship is instead characterised by high and low variance periods. Imposing a constant variance gives evidence of a bubble for the 2, 3 and 12 month lease rates, but no bubble when we use the 1 and 6 month rates as determinants.