Andy Bebut, a/k/a Theroxylandr, has this post at his blog describing an important relationship between stocks and bonds:

Back in 2007 I was writing that during the Kondratieff Spring, Summer and Autumn Treasury bonds and stocks are trading generally in the same direction, with bonds leading. During the Winter they are trading in opposite direction.

Andy's full blog is as always well worth reading, but I wanted to elaborate on the important difference in how stocks and bonds have behaved during the last 10+ years, vs. how they behaved during the great bull market of the 1980s and 1990s.