Why are stock prices so volatile outside trading hours (after hours or pre-market)?

External question — Personal Finance Stack Exchange Author: Sam Original post: https://money.stackexchange.com/questions/126678 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. I understand that companies release earnings once a quarter, and when they do, their stock price fluctuates wildly outside of trading hours based on their results. And there are external factors such as pandemics, international tensions, etc not directly related to stocks that could also affect the market after-hours. But I'm curious why it seems that even during most other days, the stock price seems to fluctuate wildly outside of trading hours, even when there are no other major events that seem to affect the stock market. Particularly, it seems most of the movement in the stock market seems to happen outside trading hours, either pre-market or after hours. Why does the stock market move so much at those times, and not during regular trading hours?