Consider the situation in which you wish to invest in a particular stock, Lucent. However, you have no cash and must sell a position in another stock in order to buy the Lucent shares. You can sell either of two stocks you hold, Microsoft or IBM. IBM has earned a 20% return since you purchased it, while Microsoft has lost 20%. Which stock do you sell? Selling IBM validates your good decision to purchase it in the first place. You enjoy pride at locking in your profit. Selling Microsoft at a loss means realizing that your decision to purchase it was bad. You would feel the pain of regret. The disposition effect predicts that you will sell the winner, IBM. Selling IBM triggers the feeling of pride and avoids the feeling of regret.
It’s common sense that because of this you may sell your winners more frequently than your losers. Why is this a problem? One reason that this is a problem is because of the U.S. tax code. The taxation of capital gains causes the selling of losers to be the wealth maximizing strategy. Selling a winner causes the realization of a capital gain and thus the payment of taxes. Those taxes reduce your profit. Selling the losers gives you a chance to reduce your taxes, thus decreasing the amount of the loss. Reconsider the IBM/Microsoft example and assume that capital gains are taxed at the 20% rate. If your positions in Microsoft and IBM are each valued at $1,000, then the original purchase price of IBM must have been $833 to have earned a 20% return. Likewise, the purchase price of Microsoft must have been $1,250 to have experienced a 20% loss. Table 5.1 shows which stock would be more advantageous to sell when you look at the total picture.
If you sell IBM, you receive $1,000, but you pay taxes of $33, so your net gain is $967. Alternatively, you could sell Microsoft and receive $1,000, plus gain a tax credit of $50 to be used against other capital gains in your portfolio; so your net gain is $1,050. If the tax rate is higher than 20% (as in the case of gains realized within one year of the stock purchase), then the advantage of selling the loser is even greater. The disposition effect predicts the selling of winners. However, it is the selling of losers that is the wealth-maximizing strategy!
This is not a recommendation to sell a stock as soon as it goes down in price—stock prices do frequently fluctuate. Instead, the disposition effect refers to hanging on to stocks that have fallen during the past six or nine months, when you really should be considering selling them. This is a psychological bias that affects you over a fairly long period of time.
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