According to Hirsch: "as January goes, so goes the year." The well known January Barometer holds that what the S&P 500 does dur­ing January will determine what kind of year the market as a whole will have. Another variation on that theme is the belief that the direction of the S&P 500 during the first 5 trading days of the year gives some hint of what's ahead for the year. The January Barometer shouldn't be confused with the January Effect, which is the tendency for smaller stocks to outperform larger stocks during January.