Arbitrage is the simultaneous purchase and sale of securities or foreign exchange in two different markets; a process of identifying market inefficiencies.

In 1954, a temporary shortage of cocoa in US caused its price to increase from 5 cents to 60 cents per pound, a whopping 12 times.

As a result, Rockwood & Co., a brooklyn based chocolate products company, found itself in a sweet spot. They were sitting on 13 million pounds of excess inventory of cocoa which instantaneously became a huge asset because of cocoa price increase.

So selling the inventory to make a handsome profit was a no-brainer except that there was just one catch to it. Rockwood & Co. followed LIFO (last in first out) inventory valuation which would have created a 50% tax liability on profits from sale of inventory.

Buffett in his early 20s

So to avoid this tax, they came up with an ingenious way to exploit the temporary opportunity. They extended a share buyback offer which allowed the shareholder to tender a share in exchange for 80 pounds of cocoa. This maneuver, according to 1954 tax code, was perfectly legal and didn’t invite heavy tax liability.

This caught the attention of a 24 year old investment analyst who was working in New York for Graham Newman Corp. It was obvious to him that one could buy Rockwood shares for $34, sell them back to the company for 80 pounds of cocoa beans (worth $36), and then sell the cocoa beans making an instant profit of $2. Considering the transaction could be done in less than a week, it worked out to a sky-high annualized return.

“For several weeks I busily bought share, sold beans, and made periodic stops at Schroeder Trust to exchange stock certificates for warehouse receipts.”, recounts Warren Buffett, the protagonist in the story above, “The profits were good and my only expense was subway tickets.”

What Buffett did is called an Arbitrage. It’s a process of identifying market inefficiencies. The classic idea is that of buying an item in one place and selling it in another. In the very early days the word applied only to the simultaneous purchase and sale of securities or foreign exchange in two different markets.

Mohnish Pabrai, in his wonderful book The Dhandho Investor, explains –

Arbitrage is classically defined as an attempt to profit by exploiting price differences in identical or similar financial instruments. For example, if gold is trading in London at $550 per ounce and in New york at $560 per ounce, assuming low frictional costs, an arbitrageur can buy gold in London and immediately sell it in New York, pocketing the difference.

Read more here:
http://www.safalniveshak.com/latticework-of-mental-models-arbitrage/