This observation was found on Financial Sense, written by Robert McHugh.
Stocks are approaching a typically Bearish seasonal time, from the last few days of December through the end of January. This new wrinkle for the "January Effect" is reason for caution. Measureable declines, several of which were significant, have started the last week of December, or in January, in 8 of the past 10 years, with a ninth top occurring in early February in 2007. If you include 2007, that is 9 out of the past 10 years.
The article is titled A New Wrinkle for the "January Effect" in Stocks .