Broker Check

Not Rocket Science

March 26, 2014
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Not Rocket Science
Jim Parker
Outside the Flags
Vice President

When the media raises the subject of beating the market through astute stock picking, the name Warren Buffett is usually cited. But what does this legendary investor actually say about the smart way to invest?
Buffett is considered to have such a track record of picking stock winners and avoiding losers that his annual letter to shareholders in his Berkshire Hathaway conglomerate is treated as a major event by the financial media.1

What does he think about the Federal Reserve taper? What could be the implications for emerging markets of a Russian military advance into Ukraine? What does an economic slowdown in China mean for developed markets?

Buffett has a neat way of parrying these questions from journalists and analysts. Instead of offering instant opinions about the crisis of the day, he recounts in his most recent annual letter a folksy story about a farm he has owned for nearly 30 years.2

Has he laid awake at night worrying about fluctuations in the farm’s market price? No, says Buffett, he has focused on its long-term value. And he counsels investors to take the same sanguine, relaxed approach to liquid investments such as shares as they do to the value of their family home.

“Those people who can sit quietly for decades when they own a farm or apartment house too often become frenetic when they are exposed to a stream of stock quotations,” Buffett said. “For these investors, liquidity is transformed from the unqualified benefit it should be to a curse.”

While many individuals seek to ape Buffett in analyzing individual companies in minute detail in the hope of finding a bargain, he advocates that the right approach for most people is to let the market do all the work and worrying for them.

“The goal of the non-professional should not be to pick winners,” Buffett wrote in his annual letter. “The ‘know-nothing’ investor who both diversifies and keeps his costs minimal is virtually certain to get satisfactory results.”

As to all the predictions out there about interest rates, emerging markets, or geopolitics, there will always be a range of opinions, he says. But we are under no obligation to listen to the media commentators, however distracting they may be.

“Owners of stocks . . . too often let the capricious and irrational behavior of their fellow owners cause them to behave irrationally,” Buffett says. “Because there is so much chatter about markets, the economy, interest rates, price behavior of stocks, etc., some investors believe it is important to listen to pundits—and, worse yet, important to consider acting upon their comments.”

The Buffett prescription isn’t rocket science, as one might expect from an unassuming, plainspoken octogenarian from Nebraska. He rightly points out that an advanced intellect and success in long-term investment don’t necessarily go together.

“You don't need to be a rocket scientist,” he has said. “Investing is not a game where the guy with the 160 IQ beats the guy with 130 IQ.”3

1. “Buffet Warns of Liquidity Curse,” Bloomberg, Feb 25, 2014.

2. Berkshire Hathaway Inc. shareholder letter, 2013,

3. “The wit and wisdom of Warren Buffett,” Fortune, November 19, 2012,

Sovereign Debt Ratings and Stock Returns

In early August, Standard & Poor’s downgraded US government debt from a top-rated AAA to AA+.1 In the weeks preceding the event, some market observers expected a downgrade to result in higher interest rates and lower stock returns.

After the downgrade, yields on US government securities fell across the term spectrum as investors around the world fled to the safe haven of US bonds. US stocks experienced negative returns in the following weeks but logged positive performance from the day of the downgrade to month end.2

These events raise questions about whether changes in sovereign debt ratings impact the financial markets. The short answer is that results are mixed, and that many other factors affect a country’s cost of capital and stock market returns.

Regarding bond markets, history offers examples of major developed countries that experienced a credit downgrade without a significant rise in interest rates.3 Examples include Australia, Canada, and Japan, which lost their top ratings in 1986, 1992, and 1998, respectively.

Other research suggests that countries with high credit ratings may withstand a downgrade better than countries with lower ratings. One study looked at sovereign credit rating downgrades since 1990 and found that bond yields changed little among countries downgraded from the highest triple-A rating. However, countries with lower credit ratings (single A or below) experienced significant interest rate increases following their downgrade.4

Stock market impact

Another question is whether the US downgrade has played a role in the US market downturn—and research does not provide convincing evidence.

Below is a chart that summarizes stock market performance of respective countries before and after a ratings change. It is based upon a study of ratings changes made by Moody’s from 1983 to 2009. During the twenty-seven-year period, the ratings agency made seventy-one upgrades and twenty-five downgrades to governments in the developed and emerging markets tracked by MSCI.

The study identified the date of each change and logged each country’s market performance in the twelve months before and twelve months after the event. Each country’s market returns were compared to the respective market index and the excess return averaged for all events. (Excess return refers to performance above or below the respective market index, either MSCI EAFE or MSCI Emerging Markets, as appropriate.)

Figure 1. Equity market performance before and after Moody’s ratings changes


Analysis conducted by Dimensional Fund Advisors using sovereign bond rating data from Moody’s Investors Services, “Sovereign Default and Recovery Rates, 1983–2009.” Returns are in US dollars and represent performance in excess of MSCI EAFE Index for developed markets and MSCI Emerging Markets Index for emerging markets. A positive excess return indicates market outperformance; a negative excess return indicates underperformance. The table reports the return of an equal-weighted, event-time portfolio. Past performance is no guarantee of future results.

The aggregate results show that stock markets of upgraded countries outperformed their respective market index in the twelve months before the rating change (13.83%), while stocks in downgraded countries aggregately underperformed the market index before the event. However, cumulative returns in the twelve months following a ratings change were almost the same for the upgraded and downgraded countries (3.87% vs. 3.73%).5

These results suggest that market prices reflect all available information and expectations about a country’s economic prospects—including the possibility of a ratings change. By the time a country’s debt rating is upgraded or downgraded, the market has already integrated the news into prices. Stock markets reflected positive economic developments prior to a ratings upgrade and negative developments before a ratings downgrade. After the event, markets did not appear to perform much differently, in aggregate.


This research underscores the importance of looking to market prices for signals about the fiscal health and prospects of a country or a company. Based on the foregoing analysis, markets appear to work faster and more accurately than ratings firms to assess a country’s financial condition and evaluate the potential impact on its cost of capital and equity market.


1. A sovereign credit rating is an assessment of a government’s ability to pay its debts. The US had held S&P’s top rating since 1941. S&P made the announcement after business hours on Friday, August 5, but word of the downgrade leaked during the day. Although timing of the announcement was a surprise, the downgrade was mostly expected, as S&P had issued a negative long-term outlook for the US in April and July. The other top credit agencies, Moody’s Investors Service and Fitch Ratings, have maintained top ratings for the US.

2. Two weeks following the downgrade, the US market, as measured by the Russell 3000 Index, logged a negative 6.82% return (August 5– 19). However, from the day of the announcement to month end, the market returned a positive 1.6%. Russell data copyright © Russell Investment Group 1995–2011, all rights reserved.