Edwards and Canter conclude that permanent changes in the behavior of
basis are possible and have occurred in other futures markets. As evidence,
they cite experience with two other commodity futures contracts: soybeans
and copper. Both markets were characterized by backwardation from 1965 to
1975, but then began exhibiting persistent contango. Thus, while a stack-androll
hedging strategy for either commodity would have produced positive cash
flows on average before 1975, such a strategy would have lost money consistently
over the ensuing ten-year period—meaning that a hedger employing a
stack-and-roll strategy of the type used by MGRM in either soybean or copper
futures markets would have experienced large and persistent losses after 1975.