This paper aims to bridge the gap between processes where shocks are permanent and those with transitory shocks by formulating a process in which the long run impact of each innovation is time varying and stochastic. Frequent transitory shocks are supplemented by occasional permanent shifts. The...

Periodically, the global economy experiences great commodity booms and busts, characterized by a broad and sharp comovement of commodity prices. There have been two such episodes since the Korean War. The first event peaked in 1974 and the second in 2008, 34 years apart. Both created major...