And the value of these unsold homes in the U.S. now exceeds (a) half-trillion dollars -- up 33 percent from a year ago!

The principle of it seems almost like an oxymoron. Most agents don't like it.

We are starting with stocks fully valued and short- and long-term interest rates still hovering near four-decade lows. Large bull-market moves are generally accompanied by, or preceded by, declining rates, and we don't have that scenario today.

In a maturing bull market, expectations are usually running at high levels for both economic growth and corporate earnings. And the higher the expectations, the greater the room for disappointment.

The good news is that most of those that made it through three years did manage to extend another full year.

Of the 14 bull markets in the S&P 500 index over the past 75 years, fewer than half have lived to celebrate a fourth anniversary.