The probability for a negative full year return in the S&P 500 if January ends in the red is 57 % vs. 31 % unconditionally. These are the years where the S&P 500 went through the worst starts to January and their corresponding January returns and full year performance:
Year Jan perf Full yr. perf
2009 -8.57 % 23.45 %
1970 -7.65 % 0.10 %
1960 -7.15 % -2.97 %
1990 -6.88 % -6.65 %
1939 -6.39 % -5.18 %
1978 -6.15 % 1.06 %
2008 -6.12 % -38.49 %
2000 -5.09 % -10.14 %
2016 -5.07 % ??? %
1977 -5.05 % -11.50 %
For the above sample of worst starts to January years excluding 2016 the average February to December return was 1.18 % and the average full year return was negative 5.58 %. This may indicate that it is probable that 2016 will not be a great year for US equities.
On the other hand we have seen recent poor S&P 500 January performance turning into great bull years as well:
Year Jan perf Full yr. perf
2009 -8.57 % 23.45 %
2003 -2.74 % 26.38 %
2010 -3.82 % 12.78 %
Source: Haver Analytics and Yardeni Research Inc.
Disclosure: I wrote this article myself, and it expresses my own opinions. I am not receiving any compensation for it.