Porfolio Standard Deviation from Time Series

Overview

The net asset value of a portfolio is just a time series like any other. The standard tools of time series analysis applies.

In particular, portfolio NAV is a non-stationtary series. This typically means that the NAV series is differenced first (by computing returns) prior to analysis. Then, the volatililty of the portfolio can be computed, and a factor analysis can be performed to try to forecast returns.

Challenges

The primary challenge to analyzing a portfolio as a typical time series is that the composition of the portfolio will very likely change over time, which casts into doubt whether assuming that the portfolio returns is generated from a stable distribution.