117. Richards & Co. Analysts has recently published a study claiming that the benefits
to diversification are constant. In other words, adding one more stock to a three stock
portfolio will have the same impact as adding one more stock to a 500‐stock portfolio.
You are not convinced and you decide to evaluate the claim.
a . Assume that all the stocks have the same standard deviation, 10 percent, and all are
independent (correlation equals 0.0). Create equally weighted portfolios of 1 to 10
stocks and calculate the standard deviation for each portfolio. Graph the portfolio
standard deviation as a function of the number of stocks. Based on the results of your
analysis, evaluate the Richard & Co. Analysts ’ claim.
b . As the number of firms increases, what do you expect will happen to the risk of the
portfolio? Can the risk of the portfolio come close to zero?
Answer:
a. Sample data from Excel:
The formulas used:
Row