The IRS lets investors offset capital gains with capital losses. These are separated into two groups, long-term and short-term. At the end of the year (December) investors often dump stocks they lost money on in order to offset their capital gains of the same group. These investors have to wait a month before re-purchasing shares otherwise those losses will be disallowed (called a Wash sale). For this reason later in the money of January a historical trend of putting the money back to use occurs, often buying back the losing stocks because there was some anticipation of future gains.