We tested every cross above the 10, 20, 50, and 200-day lines, and simply being above them, over 22 years. The crosses lag, and being above the average just means VIX is already elevated.
It is one of the first things people put on a VIX chart: a moving average or two, with the idea that when VIX trades above them, volatility's trend has turned up and a spike may be brewing. It comes in two flavors. The cross, where VIX pushes up through the line, gets read as a trigger. The state, where VIX simply sits above the line, gets read as a regime. We tested both, for the 10, 20, 50, and 200-day averages, across 22 years of daily history, against the only thing that matters: a plain baseline.
Neither holds up, and the reasons are worth seeing, because they are the two classic ways a VIX chart signal fools you.
| Cross above the... | Fires per year | VIX already up (prior 10d) | VIX peak, next 20d | Reached VIX 30 |
|---|---|---|---|---|
| 10-day MA | 27 | +1% | +22% | 22% |
| 20-day MA | 19 | +5% | +24% | 22% |
| 50-day MA | 14 | +7% | +27% | 23% |
| 200-day MA | 10 | +11% | +19% | 18% |
Run your eye down the last two columns and compare them to the baseline (+23% peak, reached 30 in 23% of cases). The crosses hug it. None meaningfully beats a random day, and the slowest one, the 200-day cross, is actually below baseline on both counts. Crossing above the long-term average is followed by less spike than average, not more.
The "already up" column explains why, and it is the heart of the matter. A moving average lags by construction, and the slower the average, the longer VIX has to have been rising before it can climb over the line. By the 10-day cross, VIX has barely moved (+1%). By the 200-day cross, it is already up 11% over the prior two weeks, and up about 10% on the day of the cross itself. The slower the line, the later the signal, and the more of the move is already behind you. The 200-day cross fires near the top, which is exactly why what follows it is reversion, not continuation.
Maybe the cross is the wrong way to use it, and what matters is simply being above the line. Here the numbers look, at first, like a real signal.
| Where VIX is sitting | Reached VIX 30+ | S&P fell 5%+ | Median VIX gain |
|---|---|---|---|
| Any day (baseline) | 23% | 20% | +23% |
| Above the 200-day MA | 42% | 31% | +19% |
| Above all three (20/50/200) | 44% | 32% | +19% |
| Below all three | 9% | 13% | +25% |
When VIX is above all of its averages, it reaches 30 in the next month 44% of the time, nearly double the baseline, and the S&P falls 5% half again as often. That looks like the signal we were after. It is not, and the last column is why.
The median VIX gain when above the averages is +19%, slightly below the +23% baseline. And when VIX is below all of its averages, the calmest possible tape, the median gain is the highest of the lot at +25%. Read that twice. The biggest relative spikes start from calm, not from "above the averages." So the higher "reached 30" rate above the line is not a bigger move, it is a shorter distance. "Above the 200-day average" is a roundabout way of saying VIX is already elevated and sitting close to 30, so it crosses 30 more often. And elevated vol clusters near drawdowns. Both are descriptions of where the market already is, not forecasts of where it is going.
"VIX is above its 200-day average" is a fancy way of saying "VIX is elevated." It tells you where you are, not where you are headed. The higher spike count that follows is proximity to 30 plus volatility clustering, the same trap that makes any elevated-VIX zone look predictive.
Four moving averages, both the cross and the state, an out-of-sample split, all measured against a plain baseline.
Crossing above the 10, 20, or 50-day line leaves forward odds essentially unchanged. The 200-day cross is actually below baseline.
The more VIX had already risen by the cross, from +1% at the 10-day to +11% at the 200-day, the worse the forward result. The slow crosses catch the top.
Above the averages reaches 30 more often, but the median percent spike is flat-to-lower, and the biggest moves start from below the lines. Proximity, not prediction.
The 20-day cross's tiny difference flips sign between the two halves of the sample, and the "it called 2018" hits are the usual base-rate illusion.
Two more checks, because a deep dive is not done at the first table. First, out of sample. We split the 22 years in half and re-ran the 20-day cross. In the first half (2004 to 2015) it landed slightly below baseline. In the second half (2015 to 2026) slightly above. A "signal" whose sign flips between the two halves is not a signal, it is noise taking turns.
Second, the famous-cases test, which is where this kind of indicator usually earns its reputation. A 20-day cross did fire before each big unwind: 16 trading days before Volmageddon, 2 days before the COVID crash, 15 days before the August 2024 unwind. Impressive, until you remember the 20-day cross fires about 19 times a year. When something fires that often, there is almost always a recent one before any event you can point to. The cross did not pick the spikes. It fired constantly, and the spikes followed a handful of them. The rest fired into nothing.
The two ways a VIX moving-average signal fools you, and how to catch it.
A moving average is, by definition, a smoothed version of the past. The cross above it always arrives after the move has started, and the slower the line, the later it is. You cannot get an early warning out of a deliberately delayed input.
Being above the moving averages mostly just means VIX is elevated. It reaches 30 more often because it is already near 30, and elevated vol travels with drawdowns. That describes the present, it does not predict the future.
When an absolute hit rate looks high, ask whether it is size or just distance: here the biggest percent spikes actually start from below the averages. And always split the sample. An edge that shows up in one half and vanishes in the other was never there.
We test popular signals the honest way: every instance counted, every result measured against a plain baseline. See what else held up, and what did not.
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