The opposite market condition to contango is known as backwardation. The opposite market condition to normal backwardation is known as contango. Economic theory regarding backwardation and contango is associated with John Maynard Keynes and John Hicks. July tomatoes are effectively a different commodity from January tomatoes (contrast contango and backwardation). Backwardation very seldom arises in money commodities like gold or silver. This makes it possible for backwardation to be observable. There may be few such parties if short-term demand exceeds supply, leading to backwardation. The term "backwardation", when used without the qualifier "normal", can be somewhat ambiguous.