If you have seen the classic Eddie Murphy/Dan Aykroyd/Jamie Lee Curtis movie Trading Places — or, if you are simply knowledgeable about commodities trading — you probably know what “futures” and “shorting” are. If not: a “future” is a contract to buy a certain commodity at a pre-set date in the future at a price set today.  The buyer of this contract hopes that the commodity’s price will go up in the interim while the contract’s seller hopes it will go down. “Shorting” (or “short selling”) happens when a seller of a stock or, in this case, of a futures contract, does not yet own what he or she is selling. Instead, the seller borrows the commodity futures from their owner, sells them, and then repurchases them later.  (This picture may help.)  The short seller hopes that the price of the commodity will go down between when he or she borrows it and when he or she repurchases it, thereby making a pretty penny on the difference.

In the movie, Aykroyd and Murphy, and various points, are trading futures of pork bellies and frozen concentrated orange juice.  In fact, futures of almost all commodities can be purchased on public markets.  Almost all, because in the United States at least, onion futures are prohibited from trade — thanks to Dwight Eisenhower, Gerald Ford, and a pair of traders who gamed the system and walked away millionaires.

In 1955, onions made up twenty percent of the commodities traded at the Chicago Mercantile Exchange, pictured above.  Two traders, Sam Seigel and Vincent Kosuga, saw an opportunity.  The pair began buying onions and onion futures in huge amounts, cornering the market -- by that fall, they ended up with roughly 98% of all the onions in Chicago, totaling roughly 30 million pounds of the vegetable.

Soon after, Seigel and Kosuga started to short sell onion futures, effectively betting that the price of onions was about to drop precipitously.  This was not a blind gamble, however.  The pair began to sell their stockpiled onions, causing a glut of supply, and forcing the price of onions down -- way down. In August 1955, a 50-pound bag of onions in Chicago cost about $2.75.  By March of 1956 (when onion season ended), due to Seigel and Kosuga's market manipulation, the going rate in Chicago for the same amount of onions was a mere 10 cents.  The pair walked away millionaires and left the onion market in shambles -- worthless in Chicago and impossible to find everywhere else.  The onion producers were going out of business and turned to Congress.

Gerald Ford, then a Congressman from Michigan, sponsored a bill outlawing the trade of onion futures -- a very specific bill aimed at preventing this very specific type of endeavor.  The commodities trading lobby, of course, stood opposed to the bill, threatening litigation if it were signed into law.  President Eisenhower called their bluff, signing the Onion Futures Act in the summer of 1958.  The Mercantile Exchange sued, and lost.  The trading of onion futures is banned in the United States to this day.

But the movie industry, at least, is better off for it.  Because the Onions Future Act robbed the Mercantile Exchange of a robust market -- and therefore, profit center -- its leadership needed to expand the offerings in order to maintain a healthy business. The two most notable additions were pork bellies and frozen concentrated orange juice -- the two key items dealt in Trading Places.