An average of a financial portfolio over time won’t be a good measure of risk taking during that time period. Consider, for example, a portfolio of two securiti

An average of a financial portfolio over time won’t be a good measure of risk taking during that time period. Consider, for example, a portfolio of two securities A and B who have mostly offsetting risk. If you own one million units of A on Jan 1 and zero units on Dec 31, but the opposite is true for B, while the average holdings over the year appear not risky, the risk on Jan 1 or Dec 31 is extreme.