Back spread. A term used in an arbitrage operation in a commodity (grain, cotton or coffee, etc.)
and also in a stock when different prices prevail normally as well as from fluctuations for the same
thing in different markets.
The thing is bought in one market and simultaneously sold in another, to be subsequently sold
where is was bought and simultaneously bought where it was sold.

In grain there is normally a difference in price between two markets equal to the cost of
transporting the grain from the market where the lower price prevails to the market where the
higher price prevails. To permit a back spread the difference in price between the two markets
must be less than the normal difference.

As an example of a back spread grain may be sold in Chicago and bought in New York if the price
in New York is not sufficiently above the price in Chicago to equal the cost of transportation of the
grain from New York to Chicago.