The preceding discussion about arbitrage makes a small discussion of fficient market theory?(EMT) also seem relevant. This doctrine became highly fashionable - indeed, almost holy scripture in academic circles during the 1970s. Essentially, it said that analyzing stocks was useless because all public information about them was appropriately reflected in their prices. In other words, the market always knew everything. As a corollary, the professors who taught EMT said that someone throwing darts at the stock tables could select a stock portfolio having prospects just as good as one selected by the brightest, most hard-working security analyst. Amazingly, EMT was embraced not only by academics, but by many investment professionals and corporate managers as well. Observing correctly that the market was frequently efficient, they went on to conclude incorrectly that it was always efficient. The difference between these propositions is night and day.
In my opinion, the continuous 63-year arbitrage experience of Graham-Newman Corp. Buffett Partnership, and Berkshire illustrates just how foolish EMT is. (There plenty of other evidence, also.) While at Graham-Newman, I made a study of its earnings from arbitrage during the entire 1926-1956 lifespan of the company. Unleveraged returns averaged 20% per year.
Starting in 1956, I applied Ben Graham arbitrage principles, first at Buffett Partnership and then Berkshire. Though Ie not made an exact calculation, I have done enough work to know that the 1956-1988 returns averaged well over 20%. (Of course, I operated in an environment far more favorable than Ben; he had 1929-1932 to contend with.)
All of the conditions are present that are required for a fair test of portfolio performance: (1) the three organizations traded hundreds of different securities while building this 63-year record; (2) the results are not skewed by a few fortunate experiences; (3) we did not have to dig for obscure facts or develop keen insights about products or managements - we simply acted on highly-publicized events; and (4) our arbitrage positions were a clearly identified universe - they have not been selected by hindsight.

Over the 63 years, the general market delivered just under a 10% annual return, including dividends. That means $1,000 would have grown to $405,000 if all income had been reinvested. A 20% rate of return, however, would have produced $97 million. That strikes us as a statistically-significant differential that might, conceivably, arouse one curiosity. Yet proponents of the theory have never seemed interested in discordant evidence of this type. True, they don talk quite as much about their theory today as they used to. But no one, to my knowledge, has ever said he was wrong, no matter how many thousands of students he has sent forth misinstructed. EMT, moreover, continues to be an integral part of the investment curriculum at major business schools. Apparently, a reluctance to recant, and thereby to demystify the priesthood, is not limited to theologians.
Naturally the disservice done students and gullible investment professionals who have swallowed EMT has been an extraordinary service to us and other followers of Graham. In any sort of a contest - financial, mental, or physical - it an enormous advantage to have opponents who have been taught that it useless to even try. From a selfish point of view, Grahamites should probably endow chairs to ensure the perpetual
teaching of EMT.

All this said, a warning is appropriate. Arbitrage has looked easy recently. But this is not a form of investing that guarantees profits of 20% a year or, for that matter, profits of any kind. As noted, the market is reasonably efficient much of the time: For every arbitrage opportunity we seized in that 63-year period, many more were foregone because they seemed properly-priced.