Market observers are well aware that we have been stuck in a "sideways market" for quite a while, without a major move up or down since the S&P 500 fell into the low-mid 1800s in mid-October. That means the sideways market has lasted over six months now: From the November 6, 2014 close of 2031, the index has not moved more than +4.6% above (2125) or -2.9% below (1972) that level since then.

Over the past six months the S&P 500 has moved very little in either direction from its level in early November. Chart courtesy of StockCharts.com

Over the past six months the S&P 500 has moved very little in either direction from its level in early November. Chart courtesy of StockCharts.com

Such periods were common enough in the slow-moving phase of the bull market from early 2004 to mid-2006, but they have been exceedingly rare since then -- the last time the Fed raised interest rates, by the way. In fact, Dr. Strangemarket can find only one six month period since then with such small market moves in either direction:

The only other time since 2006 that the market has stayed sideways for so long: February 1 - August 1, 2011. Chart courtesy of StockCharts.com

The only other time since 2006 that the market has stayed sideways for so long: February 1 - August 1, 2011. Chart courtesy of StockCharts.com

This chart shows the movement of the S&P 500 from February 1 to August 1, 2011. At the beginning of February the index stood at 1307, and for the next six months it moved barely 4% in either direction.

Then suddenly at the beginning of August 2011, in just a single week the market plunged 13%.

Now Dr. Strangemarket is not predicting a 13% drop in the stock market next week. The point is to note that the current prolonged sideways market is very rare in the past decade, and it can end suddenly.