VANGUARD GNMA FUND INVESTOR SHARES VFIIX

A rolling return for a period such as 5-year, as of a specific date, represents the investment’s performance over the preceding five years leading up to that date. In the 5-year rolling chart, the value on any given date corresponds to the annualized return for the preceding 5 years up to that very date. Thus, for instance, the chart value on 8/28/2015 reflects the annualized return from 8/28/2010 to 8/28/2015. A 5-year rolling return chart for an investment (stock, fund or portfolio) depicts the return sequence of 5-year trailing returns for the dates in the chart.

These rolling returns contrast with the most recent 3, 5, 10, and 15-year returns, as they solely depict the returns for those respective periods leading up to the most recent date, without encompassing every date in the historical record.

Rolling return charts offer a more precise insight into a portfolio’s risk and return stability (including funds or individual stocks). This is particularly true when focusing on the minimal return points within a rolling return chart as a measure of a fund or a portfolio's risk. A well-known observation, often attributed to ‘Murphy’s law’, is that it tends to perform poorly when investors decide to follow an investment due to its recent strong returns. Sound familiar? Information regarding minimum rolling returns could help mitigate this predicament. Investors can opt for an investment showcasing high minimum rolling returns within their preferred holding durations. In fact, merely possessing knowledge of such minimum rolling period returns can anchor investors’ expectations.

For instance, let’s consider an investor who follows a model portfolio (or even simply purchases and holds a fund like VFINX or SPY) for 10 years. Armed with knowledge of this portfolio’s minimum 10-year rolling return since its inception date or the fund’s inception (in the case of VFINX, recognizing that the minimum 10-year rolling return since 1987 could be as low as -2.24%), the investor should reasonably anticipate the potential for the portfolio to incur losses over the forthcoming 10 years.

Minimum rolling return for a period such as 10-year offers a different and often better historical risk and return metric than other popular risk and return metrics such as Sharpe ratio, standard deviation (volatility) or maximum drawdown.

See Portfolio Calculator and Rolling Returns for more detailed description.