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1. What is the partfolio nisk of holding 11 positions with identi cal volatility

ID: 1122004 • Letter: 1

Question

1. What is the partfolio nisk of holding 11 positions with identi cal volatility (any arbitrary volatility) wath one position being 50% ofthe portfolio and the remaining 10 being 5% each? Assume positions are uncorrelated. There are two approaches to thisproblem The direct approach works ith all 11 positions at once. The indirect approach considers a portfolio of portfolios. The following questions assume there are three risky asset classes in the economy Market Capitalization $ trillion) Volatility 20 15 Beta Asset Small Cap Equity Large Cap Equity Corporate & Govt Bonds 1.9 12 20 0.4 2. What are the weights and beta of the market portfolio?

Explanation / Answer

1)

Portfolio risk is measured by standard deviation, which is also known as volatility. It's the deviation of returns from its mean.

Formula: Standard deviatio = Squared-root of Variace
Variance of a Portfolio = [(Variance of stock A * Weight of Stock A)2 + [(Variance of stock B * Weight of Stock B)2+ (2 x Weight of Stock A x Weight of Stock B x Standard Deviation of Stock A x Standard Deviation of Stock B x Co-Relation coefficient of both stocks)]

Since no infomration related to proportion of each position is given, we assume that every position has equal proportion. So, weihgt of each position in portfolio = 1/11 = 0.090909 or 9.0909%

Also, as the positions are uncorelated, co-relation coefficient of the positions will be 0.

Variance of position with 50% volatility = 0.502 = 0.25
Variance of all other positions = 0.052 = 0.0025

Variance of portfolio = (0.090909 x 0.25)2 + (0.0090909 x 0.0025)2 + (0.0090909 x 0.0025)2 + (0.0090909 x 0.0025)2 + (0.0090909 x 0.0025)2 + (0.0090909 x 0.0025)2 + (0.0090909 x 0.0025)2 + (0.0090909 x 0.0025)2 + (0.0090909 x 0.0025)2+ (0.0090909 x 0.0025)2+ (0.0090909 x 0.0025)2 = 0.000517

Portfolio Risk = (0.000517)0.5 = 0.022739