KEY POINTS
  • A gain in January has foretold an annual gain 87 percent of the time with only 9 major errors going back to 1950, according to the Stock Trader's Almanac.
  • The S&P 500 was up 7.9 percent in January, its best performance for the first month of the year since 1987.
  • Some market pros are skeptical of the January barometer, but Jeff Hirsch, editor-in-chief of the Stock Trader's Almanac, says it makes sense because that's when Wall Street expectations are reset for the year.
The Charging Bull near Wall Street is pictured in New York.

Stocks had their best January gains in more than 30 years, and that should mean 2019 will be a pretty good year for the market.

That's what the widely watched January barometer tells you — as goes January, so goes the year. According to Stock Trader's Almanac, going back to 1950, that metric of January's performance predicting the year has worked 87 percent of the time with only nine major errors, through 2017. In the years January was positive, going back to 1945, the market ended higher 83 percent of the time, according to CFRA.