90-Day Annualized Volatility

This uses the same estimator as the thirty-day figure over a ninety-day window, which produces a steadier number built on three times as many observations. It is the more common choice when ranking assets by volatility, since it is less sensitive to a single day. It is still purely backward-looking.

计算方式

standard deviation of daily log returns over the trailing 90 days x sqrt(365) x 100

易产生误导之处

The added stability is also the weakness: after conditions change, this figure keeps reporting the previous regime for weeks and does not register a shift until roughly a third of the window has rolled through. Ninety days is long enough to contain a cliff unlock or a first listing on a major venue, and the resulting one-day move dominates the standard deviation for the following quarter. Assets whose prices update infrequently show artificially low volatility, because stale prints are recorded as zero returns rather than as missing data. The same square-root-of-365 versus square-root-of-252 inconsistency between providers applies here.

与股权的类比，以及为何该类比不成立

Ninety-day realized volatility on an equity or index; equity series pause on weekends and holidays, so a ninety-day equity window covers a longer calendar span with fewer, less extreme observations.

如何解读高值或低值

A higher figure means larger dispersion of daily returns across the quarter. Comparing it with the thirty-day figure shows whether recent dispersion is above or below the quarterly level.