S&P 500 Realized Volatility (21-day)

## What this measures

The standard deviation of the S&P 500's daily log returns over the last 21 trading days (about one month), annualized by √252 and shown in percent. Palanor computes it from licensed closing prices of SPY, the ETF that tracks the index.

## Why it matters

It is the turbulence stocks have actually delivered, where an implied measure like the VIX is the turbulence options buyers expect. Realized volatility clusters: calm months follow calm months and violent ones follow violent ones, so it is a good read of the regime the market is in right now.

## How to read it

Percent a year. Readings near 10 are a quiet market; 20 is choppy; above 30 is a sell-off regime. It reached 52 in April 2025. It runs on average a few points below the VIX, because options buyers pay a premium for protection.

## What it does not say

It looks backward over one month, so it lags turning points and says nothing about what the market expects next. SPY prices exclude dividends, which adds a small bump on ex-dividend days.

## Source

Computed by Palanor from SPY daily closes supplied under licence by a market data provider. Only the derived volatility is published, never the underlying prices. It replaces the VIX on Markets surfaces.