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Is it possible to quantify the probability of sudden big movements for a high-volume stock?
This is a classic correlation does not imply causation situation.  There are (at least) three issues at play in this question: If you are swing- or day-trading then the first and second issues can definitely affect your trading.  A higher-price, higher-volume stock will have smaller (percentage) volatility fluctuations within a very small period of time. However, in general, and especially when holding any position for any period of time during which unknowns can become known (such as Netflix's customer-loss announcement) it is a mistake to feel "safe" based on price alone. When considering longer-term investments (even weeks or months), and if you were to compare penny stocks with blue chip stocks, you still might find more "stability" in the higher value stocks.  This is a correlation alone — in other words, a stable, reliable stock probably has a (relatively) high price but a high price does not mean it's reliable. As Joe said, the stock of any company that is exposed to significant risks can drop (or rise) by large amounts suddenly, and it is common for blue-chip stocks to move significantly in a period of months as changes in the market or the company itself manifest themselves. The last thing to remember when you are looking at raw dollar amounts is to remember to look at shares outstanding.  Netflix has a price of $79 to Ford's $12; yet Ford has a larger market cap because there are nearly 4 billion shares compared to Netflix's 52m.