Can a VIX MACD Zero-Cross Predict a Volatility Spike?

It looks like it flags every major spike in advance. Overlay MACD on the VIX, wait for the line to cross above zero, and it appears to give you a clean warning a couple of weeks before the next blow-up, but 22 years of backtesting show these MACD crosses happen so often that some will naturally land a few weeks before a big spike by luck, not because they predict anything.

We took every VIX MACD zero-cross-up since 2004, all 138 of them, and measured what the VIX and the S&P 500 actually did over the next 10, 20, and 40 trading days. Then we compared those outcomes to a plain baseline: what happens after a randomly chosen day.

If the signal actually predicted anything, the VIX should have risen more and the S&P 500 should have fallen more after these crosses than after a typical day. Neither happened.

The Result: No better than a coin flip

Look across all 3 columns. The cross adds a point or two at most, well inside the margin of error. At 10 days it actually does a little worse.

“But it called 2018, 2020, and 2024.”

This is the part that fools people. A zero-cross did fire before each of those famous spikes: 14 trading days before Volmageddon in February 2018, 19 days before the COVID crash, and 13 days before the August 2024 yen-carry unwind. Three for three. It looks almost perfect.

Then count how often the signal actually fires: 138 times in 22 years, or roughly once every two months. When something triggers that frequently, there is almost always a recent cross sitting just before whatever event you decide to point at. The MACD did not select those spikes. It fired constantly, and a handful of those 138 signals happened to be followed by big moves. The other 130 or so fired into nothing.