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Comment by deadmutex | Hacker News Reader

> meaning that we get a decline like this roughly every 100 trading days, which means about twice a calendar year, very roughly.

Stock volatility is typically clustered. So, we can't make this type of claim. Just like this statement is flawed: Chicago experiences below freezing weather 10% of the time, so every 10 days you see below freezing weather.

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Just to come back and clarify: it bounced this morning. Yesterday wasn't the crash. It's not a cluster. Grandparent point was fundamentally correct. "Nothing to see here", as it were.

It happened in 2016, 2018, 2020, 2022, 2025 and 2026, so 6 out of last 11 years. Not sure if I would count it as too rare.

That's every other year, which is quite different from 2+yearly, which is exactly the point the gp was making.

"Four times every two years" isn't exactly the same as "twice every year", but also reflects a similar, "not that unusual" answer.

Although I didn't claim "twice every year like clockwork" in my top-level comment either. It's just a very basic statement of the base rate.

Make it eight-times every four years or sixteen-times every eight years. Or maybe "Four-times every other year, in a clustered fashion".

I don't think any of that really changes the point.

It does change the point! If it happened roughly twice a year, it's not as noteworthy when it happens than if tends to happen every other year, but four times.

It's more noteworthy when it happens the more clustered it tends to be. If it were typical that we'd go ~7 years with none then have ~16 in a single year, it would be huge news when it happens.

I think "every other year" is 100% of a piece with grandparent's point, which is that this is "newsworthy but not notable".

Markets move. Sometimes they move more than normal. This is one of those times.

Will it keep moving? Will it crash? Maybe! But what it has done right now is not that.

Every other year is much less frequent than twice a year?

Multiple times every other year.

'Biannual' finally found it's perfect use case.

Corrections (down 10% or more): about one per year on average. The Nasdaq is more volatile than the S&P 500, which has a correction closer to every 1.5 to 2 years.

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