A Man for All Markets: From Las Vegas to Wall Street, How I Beat the Dealer and the Market

by Edward O. Thorp

its simplest form, investors sell losing stocks before the end of the current year, realizing losses that reduce the year’s income taxes. This behavior contributes to the so-called January effect where selling pressure in December further depresses the stock prices of the year’s losers, followed by a rebound and excessive performance in January. The impact is greater for smaller companies. Investors used to realize a tax loss by selling a loser and buying it back immediately, with little risk of economic loss (or gain). To inhibit this loss of tax revenue by making it risky, the US government introduced the “wash sale rule,” which says that anyone who sells a stock at a loss and buys it back within thirty-one days may not recognize the loss for tax purposes. The rule is worded also to thwart savvy investors inclined to swap into an “equivalent” stock to get around this.