Modern Portfolio Theory and Asset Allocation [Not Correlation]



By Dr. David Edward Marcinko MBA CMP©


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Modern Portfolio Theory approaches investing by examining the complete market and the full economy. MPT places a great emphasis on the correlation between investments. 


Correlation is a measure of how frequently one event tends to happen when another event happens. High positive correlation means two events usually happen together – high SAT scores and getting through college for instance. High negative correlation means two events tend not to happen together – high SATs and a poor grade record.

No correlation means the two events are independent of one another. In statistical terms two events that are perfectly correlated have a “correlation coefficient” of 1; two events that are perfectly negatively correlated have a correlation coefficient of -1; and two events that have zero correlation have a coefficient of 0.

Correlation has been used over the past twenty years by institutions and financial advisors to assemble portfolios of moderate risk.  In calculating correlation, a statistician would examine the possibility of two events happening together, namely:

  • If the probability of A happening is 1/X;
  • And the probability of B happening is 1/Y; then
  • The probability of A and B happening together is (1/X) times (1/Y), or 1/(X times Y).

There are several laws of correlation including;

  1. Combining assets with a perfect positive correlation offers no reduction in portfolio risk.  These two assets will simply move in tandem with each other.
  2. Combining assets with zero correlation (statistically independent) reduces the risk of the portfolio.  If more assets with uncorrelated returns are added to the portfolio, significant risk reduction can be achieved.
  3. Combing assets with a perfect negative correlation could eliminate risk entirely.   This is the principle with “hedging strategies”.  These strategies are discussed later in the book.



In the real world, negative correlations are very rare 

Most assets maintain a positive correlation with each other.  The goal of a prudent investor is to assemble a portfolio that contains uncorrelated assets.  When a portfolio contains assets that possess low correlations, the upward movement of one asset class will help offset the downward movement of another.  This is especially important when economic and market conditions change.

As a result, including assets in your portfolio that are not highly correlated will reduce the overall volatility (as measured by standard deviation) and may also increase long-term investment returns. This is the primary argument for including dissimilar asset classes in your portfolio. Keep in mind that this type of diversification does not guarantee you will avoid a loss.  It simply minimizes the chance of loss. 

In the table provided by Ibbotson, the average correlation between the five major asset classes is displayed. The lowest correlation is between the U.S. Treasury Bonds and the EAFE (international stocks).  The highest correlation is between the S&P 500 and the EAFE; 0.77 or 77 percent. This signifies a prominent level of correlation that has grown even larger during this decade.   Low correlations within the table appear most with U.S. Treasury Bills.

Historical Correlation of Asset Classes

Benchmark                             1          2          3         4         5         6            

1 U.S. Treasury Bill                  1.00    

2 U.S. Bonds                          0.73     1.00    

3 S&P 500                               0.03     0.34     1.00    

4 Commodities                         0.15     0.04     0.08      1.00      

5 International Stocks              -0.13    -0.31    0.77      0.14    1.00       

6 Real Estate                           0.11      0.43    0.81     -0.02    0.66     1.00

Table Source: Ibbotson 1980-2012

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VALUATION: Approaches for Common Stocks


By Dr. David Edward Marcinko MBA CMP™

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QUESTION: We are in near bear market correction territory – especially for tech stocks – so what are the 2 major types of valuation approaches for common stock?



ANSWER: There are basically two different approaches for common stock valuation; top-down and bottom-up.  Under either of the two fundamental approaches, a physician investor will have to work with individual company data.  In reality, each of these approaches is used by investors and security analysts when doing fundamental analysis.  


With the bottom-up approach, investors focus directly on a company’s prospects. Analysis of such information as the company’s products, its competitive position, and its financial status leads to an estimate of the company’s earnings potential, and, ultimately, its value in the market.  Considerable time and effort are required to produce the type of detailed financial analysis needed to understand a firm’s standing. The emphasis in this approach is on finding companies with good long-term growth prospects, and making accurate earnings estimates. 

The top-down approach is the opposite of the bottom-up approach. Investors begin with the economy and the overall market, considering such important factors as interest rates and inflation. They next consider likely industry prospects, or sectors of the economy that are likely to do particularly well (or particularly poorly). Finally, having decided that factors are favorable for investing, and having determined which parts of the overall economy are likely to perform well, individual companies are analyzed.



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PODCAST: Healthcare Stocks, Investing & IPOs?

By Eric Bricker MD

Healthcare Stock and IPO Investing Can Be Confusing. The Story of Privia Health is a Good Case Study in Understanding the Underlying Economics in Healthcare Investing:




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