Every day I hear from the experts on CNBC-TV and the radio gurus that the way to buy stocks is find value. One mans Rembrandt is another mans connect-the-dots and fill in the spaces. Valuation is like beauty. It is in the mind of the beholder.

If valuation is the key to buying stocks then there should be some kind of a formula to determine what is undervalued and over-valued. In every industry there are formulas for standards of performance. For cars we want to know the zero to 60 miles per hour in how many seconds. For soap we want it to be 99 and 44/100 percent pure. For alcoholic beverages it could be how long it has been aged. And on and on.

Yet in the stock market we have no hard and fast set of rules by which to judge a company performance. Ah, and theres the rub! No matter how good a company performance might be it may have no bearing on the price performance of the stock. You can find good companies that are within a sector that is doing poorly and yet one company can be making huge profits and sales, but the stock price is going nowhere. There need not be any correlation.

When you are in a bull market almost every stock goes up even the dogs. When you are in a bear market almost every stock goes down even the best ones. We ended an 18 year bull market in 2000 and almost without exception every stock headed for the exit.

Bull and bear markets follow relatively standard patterns of about 16 to 18 years up and 16 to 18 years down and the valuations go right along with them. If you own stocks or especially index funds during the bear periods you will be lucky to have broken even at the end of the 16-year cycle. Cash in your mattress will outperform market returns while the bear is in charge.

During these bear times there will be periods when the market will have a nice advance such as the one we saw start in 2003. These intermediate rises can ultimately bring many investors back into the market only to lose it when the rally is over and true valuation returns.

One valuation measurement for the overall market is the Price/Earnings ratio of the S&P500 Index. The median number for the historic purposes has been around 14. Today it is running about 21 which is considered high. When bear markets end the P/E can be about 6 or 8. There are other factors to be considered when buying any stock or fund, but the one thing that is most important is to have an exit strategy. Without one you will give back your profits.

No one knows exactly where the top or bottom of a market move will be. Knowing conventional valuations is one tool to help your buying and selling decisions.