highly unlikely. A depression like situation would kill off commodities regardless of the dollar, but the dollar would prolly be strong vis-a-vis other currencies in such a situation. Other countries would probably get hammered worse. If the US was the only one in the shit house however, you could see this happen I bet. The foreign nations would also have to have slow growth stifling commodity demand.
I don't see another situation in which they both move that way.
Commodities boom and bust whenever they want. Here is a % relative chart .... it is big .... but look at '85 - '88 when the dollar was in a steady downward trend.
P.S. do not show this chart to goldbugs, they get mad.
