$5.$ The Wall Street Journal reported that the yield on common stocks is about $2$ percent, whereas a study at the University of Chicago contends that the annual rate of return on common stocks since $1926$ has averaged about $10$ percent. Reconcile these statements.

$6.$ Some financial theorists consider the variance of the distribution of expected rates of return to be a good measure of uncertainty. Discuss the reasoning behind this measure of risk and its purpose.