Many of the people who buy stocks receive year-end profit-sharing, bonuses, and other forms of variable compensation in December and January. For those at upper-income levels—i.e., those most likely to buy stocks—such bonuses are particularly crucial. (Wall Streeters get salaries throughout the year, but only "get paid" when they receive their bonuses in January.) Over time, bonuses have filtered into related areas such as law, management consulting, and the corporate world generally. And these people like to put their money to work quickly. That's why the high-end New York City apartment market gets hot in January and February. If people are feeling flush and confident about the future—even though the bonus pay might reflect the prior year's performance—what they do in January might reasonably presage what they do for the rest of the year.