The stock market is following a rare pattern that could signal double-digit gains next year

• The stock market is following a rare pattern that could signal big gains next year, NDR said.
• The S&P 500 rallied for five months straight this year, followed by three consecutive months of losses. 
• In previous instances when that's occurred, the index posted double-digit gains a year later.

A rare pattern of gains and losses in the S&P 500 is flashing a bullish signal that the benchmark index could be in for a double-digit rise in the year ahead, analysts from Ned Davis Research said in a note this week.