As investors ring in the new year, some may see the occasional headline about the “January Indicator” or “January Barometer.” This theory suggests that the price movement of the S&P 500 during the month of January may signal whether that index will rise or fall during the remainder of the year. In other words, if the return of the S&P 500 in January is negative, this would supposedly foreshadow a fall for the stock market for the remainder of the year, and vice versa if returns in January are positive.
So have past Januarys’ S&P 500 returns been a reliable indicator for what the rest of the year has in store? If returns in January are negative, should investors sell stocks? Exhibit 1 shows the monthly returns of the S&P 500 Index for each January since 1926, compared to the subsequent 11-month return (i.e., the return from February through December). A negative return in January was followed by a positive 11-month return about 60% of the time, with an average return during those 11 months of around 7%.
This data suggests there may be an opportunity cost for abandoning equity markets after a disappointing January. Take 2016, for example: The return of the S&P 500 during the first two weeks was the worst on record for that period, at -7.93%. Even with positive returns toward the end of the month, the S&P 500 returned -4.96% in January 2016, the ninth-worst January return observed from 1926 to 2017. But a subsequent rebound of 18% from February to December resulted in a total calendar year return of almost 13%. An investor reacting to January’s performance by selling out of stocks would have missed out on the gains experienced by investors who stuck with equities for the whole year. This is a good example of the potential negative outcomes that can result from following investment recommendations based on an “indicator.”
Exhibit 1: January Return vs. Subsequent 11-Month Return of the S&P 500 Index 1926–2017