Investors have become accustomed to bull markets -- long periods of stock price appreciation, i.e. a rising stock market. That's been the norm since the start of publicly-traded stocks in the United States, and certainly a feature of markets in the post-1980 period.

Provided that the U.S. economy is growing in a sustainable way and increasing its productive capacity, bear markets have been the exception, the momentary pull-back, when one takes a long view of the investment horizon.

The current bear market can be seen in that light, again, provided the nation's economy is on a sustainable growth track with an increasing productive capacity.

Still, the key in the above has been the U.S. economy (obviously). Absent a healthy economy, different Dow case studies pop up.

For example, what if the Dow didn't fall -- and didn't rise -- for seven years? In other words, a sideways Dow where no progress is made? It seems like a remote possibility, but that's exactly what occurred from early 1966, when the Dow fell below 1,000, until late 1972, when the Dow reclaimed the psychologically-significant 1,000 level.