A hedge is an investment position intended to offset potential losses or gains that may be incurred by a companion investment. A hedge can be constructed from many types of financial instruments, including stocks, exchange-traded funds, insurance, forward contracts, swaps, options, gambles, many types of over-the-counter and derivative products, and futures contracts.
Public futures markets were established in the 19th century to allow transparent, standardized, and efficient hedging of agricultural commodity prices; they have since expanded to include futures contracts for hedging the values of energy, precious metals, foreign currency, and interest rate fluctuations.
Hedging is the practice of taking a position in one market to offset and balance against the risk adopted by assuming a position in a contrary or opposing market or investment. The word hedge is from Old English hecg, originally any fence, living or artificial. The first known use of the word as a verb meaning 'dodge, evade' dates from the 1590s; that of 'insure oneself against loss,' as in a bet, is from the 1670s.
Optimal hedging and optimal investments are intimately connected. It can be shown that one person's optimal investment is another's optimal hedge (and vice versa). This follows from a geometric structure formed by probabilistic representations of market views and risk scenarios. In practice, the hedge-investment duality is related to the widely used notion of risk recycling.
A typical hedger might be a commercial farmer. The market values of wheat and other crops fluctuate constantly as supply and demand for them vary, with occasional large moves in either direction. Based on current prices and forecast levels at harvest time, the farmer might decide that planting wheat is a good idea one season, but the price of wheat might change over time. Once the farmer plants wheat, he is committed to it for an entire growing season. If the actual price of wheat rises greatly between planting and harvest, the farmer stands to make a lot of unexpected money, but if the actual price drops by harvest time, he is going to lose the invested money.