We use the momentum threshold autoregressive (MTAR) approach to test for speculative bubbles in US corn, soybean and wheat prices. To approximate fundamental values of these agricultural commodities, we use real crude oil prices and real exchange rates. Our empirical results support the...

Short sellers are routinely blamed for destabilizing stock markets by exacerbating deviations from fundamental values. In response, regulators periodically impose short sale constraints aimed at preventing excessive stock market declines. One explanation is that policy makers regard short...