Finance Reading: Risk and Return 1: Stock Returns and Diversification

This is the first in a set of two Readings on risk and return. It introduces the ideas of financial risk and return, at first intuitively, with a discussion of investor risk aversion and tradeoffs, and then formally, with a basic explanation of pertinent statistics. It introduces probability distributions and their parameters-mean and standard deviation-as measures of expected return and risk. Using sample statistics from historical returns as coordinate pairs, it plots asset classes in mu-sigma space to give a graphical representation of risk and return, and defines dominance. To cement understanding, the text steps through calculations of risk and return statistics from historical price data for Microsoft to mu-sigma space. The second half of the reading covers the co-movement of stock returns using sample covariance, beta, and correlation computed for pairs of risky assets. Scatter plots and linear regression are introduced to calculate beta. The Reading introduces essential portfolio math, with portfolio weights and correlation coefficients. It shows that a portfolio's risk is lower than the weighted average risk of its component assets if the assets are not perfectly positively correlated. This fundamental statistical property gives rise to the economics of diversification. The Reading contains 7 web-based Interactive Illustrations. The first demonstrates the Central Limit Theorem. The second ensures a solid understanding of how returns are calculated from prices and dividends. The third shows how to create a histogram.

• Risk management
• Investment management
• Financial analysis
• Diversification
• Profitability
• Probability
• Financial risk