Rolling 12-month return
Shows the return for the latest 12 months at each point in history.
Rolling 12-month return does not take the whole history at once; it takes the latest year again and again. It is like moving a 12-month ruler along the chart and reading what happened inside the current window.
The metric helps show whether the recent year is improving or weakening. One lifetime return number can hide the fact that the latest 12 months looked very different.
A positive value means growth over the latest year; a negative value means a loss over that yearly window. The series matters more than one spike: a sudden jump may come from one unusually strong month. The calculation needs enough history, and dividends and coupons are already inside NAV returns.
Example: over the latest 12 months, the account index grows from 1000 to 1180. The rolling 12-month return at that point is +18%. One month later, an old strong month may leave the window and a weak new month may enter, so the value can fall without a disaster.
How we compute it
We use monthly TWR returns on the unified investment-account basis. Each point compounds the trailing 12 calendar months; at least 18 monthly observations are required, and dividends/coupons are already inside NAV returns.