The Great Recession of 2008-2009 saw many investors lose huge amounts of money. The average retirement portfolio took more than a 30% hit, and the modern portfolio theory (MPT) fell out of repute, seemingly debunked by a two-year period where buy-and-hold investors saw a decade of gains wiped out in a figurative instant. The massive sell-off during 2008-2009 seemed to violate the rules of the game; after all, passive investing was not supposed to absorb losses of that magnitude.

The reality is buy-and-hold still works, even for those who held passive portfolios in the Great Recession. There is statistical proof that a buy-and-hold strategy is a good long-term bet, and the data for this holds up going back for at least as long as investors have had mutual funds.

The Logic of Buy-and-Hold Investing

"Buy and hold" does not have a set definition, but the underlying logic of a buy-and-hold equity strategy is fairly straightforward. Equities are riskier investments, but over longer holding periods, an investor is more likely to realize consistently higher returns compared to other investments. In other words, the market goes up more often than it goes down, and compounding the returns during good times yields a higher overall return as long as the investment is given sufficient time to mature.

Raymond James published an 85-year history of the securities markets to study the hypothetical growth of a $1 investment between 1926 and 2010. It noted that inflation, as measured by the controversial consumer price index (CPI), eroded more than 90% of the dollar's value, so it took $12 in 2010 for the same purchasing power as $1 in 1926. Nevertheless, $1 applied to large-cap stocks in 1926 had a market value of $2,982 in 2010; the figure was $16,055 for small-cap stocks. The same $1 invested in government bonds would only be worth $93 in 2010; Treasury bills (T-bills) were even worse at a paltry $21.

The period between 1926 and 2010 includes the recession of 1926-1927; the Great Depression; subsequent recessions in 1949, 1953, 1958, 1960, 1973-75, 1981 and 1990; the dot-com crisis; and the Great Recession. Despite a laundry list of periods of turmoil, the markets returned a compound annual growth of 9.9% for large caps and 12.1% for small caps.

Volatility and Selling Into Falling Markets

It is just as important for a long-term investor to survive bear markets as it is to capitalize on bull markets. Take the case of IBM, which lost nearly one-fifth, at 19%, of its market value between May 2008 and May 2009. But consider that the Dow fell by more than one-third, at 36%, over the same period, which means IBM shareholders did not have to recover nearly as much to see the precrash value. Reduced volatility is a major source of strength over time.

The principle is evident if you compare the Dow and IBM between May 2008 and September 2011, when markets were starting to take off again. IBM was up 38%, and the Dow was still down 12%. Compound, this kind of return over multiple decades and the difference could be exponential. This is why most buy-and-hold advocates flock to blue-chip stocks.

IBM shareholders would have made a mistake by selling during 2008 or 2009. Lots of companies saw market values disappear during the Great Recession and never recovered, but IBM is a blue-chip for a reason; the firm has decades of strong management and profitability. Suppose an investor bought $500 worth of IBM stock in January 2007 when share prices were approximately $100 a share. If he panicked and sold in the depth of the market crash in November 2008, he would have only received $374.40, a capital loss of more than 25%. Now suppose he held on throughout the crash; IBM crossed the $200 a share threshold in early March 2012 just five years later, and he would have doubled his investment.

Low Volatility Vs. High Volatility

One 2012 Harvard Business School study looked at the returns a hypothetical investor in 1968 would have realized by investing $1 in 20% of U.S. stocks with the lowest volatility. The study compared these results with a different hypothetical investor in 1968, who invested $1 in 20% of U.S. stocks with the highest volatility. The low-volatility investor saw his $1 grow to $81.66 while the high-volatility investor saw his $1 grow to $9.76. This result was named the "low-risk anomaly" because it supposedly refuted the widely cited equity-risk premium.

The results should not be all that surprising, however. Highly volatile stocks turn over more frequently than low-volatility stocks, and highly volatile stocks are less likely to follow the overall trend of the broad market, with more bull years than bear years. So while it might be true that a high-risk stock is going to offer a higher return than a low-risk stock at any single point in time, it is much more likely a high-risk stock does not survive a 20-year period compared to a low-risk stock.

This is why blue chips are a favorite of buy-and-hold investors. Blue-chip stocks are very likely to survive long enough for the law of averages to play out in their favor. For example, there is very little reason to believe The Coca-Cola Company or Johnson & Johnson, Inc. will be out of business by 2030. These kinds of companies usually survive major downturns and see their share prices rebound.

Suppose an investor purchased Coca-Cola stock in January 1990 and held it until January 2015. During this 26-year period, she would have experienced the 1990-91 recession and a full four-year slide in Coca-Cola stock from 1998 through 2002. She would have experienced the Great Recession as well. Yet, by the end of that period, her total investment would have grown 221.68%.

If she had instead invested in Johnson & Johnson stock over the same period, her investment would have grown 619.62%. Similar examples can be shown with other favorite buy-and-hold stocks, such as Google, Inc., Apple, Inc., JPMorgan Chase & Co., Nike, Inc., Bank of America Corp, Visa, Inc. and Sherwin-Williams Company. Each of these investments has experienced difficult times, but those are only chapters in the buy-and-hold book. The real lesson is that a buy-and-hold strategy reflects the long-term law of averages; it is a statistical bet on the historical trend of markets.