Jeremy Siegel, the famous Wharton School finance professor coined the phrase โ€œstocks for the long-runโ€ with his identically titled 1994 best seller, Stocks for the Long Run: The Definitive Guide to Financial Market Returns and Long-term Investment Strategies. In the book, professor Siegel looks back at up to two centuries of financial market history to support his claim that stocks are the most profitable long-term investments. And indeed his conclusion has been true.

But the good professor failed to adequately warn investors that the long run can be a really long time. Check out my stock market charts on Spain, Italy, and Greece.

Spanish stock prices are no higher than they were 13 years ago. That is a long time to forego capital gains, but in comparison to the performance of Italian and Greek stocks, the Spanish stock market looks like a winner. Italian stock prices are no higher than they were in 1986โ€”thatโ€™s 26 years without a capital gain. And Greek stocks donโ€™t look much better. The MSCI Greece index has done a round-trip over the last two decades. How do you think an Italian investor who retired in the late 1980s would have fared with a portfolio invested entirely in stocks?

Siegel may be right about the long run profitability of stocks, but the famous British economist John Maynard Keynes warned us long ago that โ€œIn the long run, we are all dead.โ€

Diversification and balance (as in bonds) remain vital to your short and long run investment success.