Chart of the day: Apple's 69-minute, $5.5 billion dropAugust 8, 2013: 4:39 PM ET
This is what it looks like when Apple goes ex-dividend.
FORTUNE -- Apple (AAPL) opened Thursday at $464.02. An hour and nine minutes later, it hit $457.95, having shed more than $5.5 billion in market value.
One never knows on Wall Street, but the most likely explanation is that traders who bought Apple for its $3.05-per-share dividend sold it as soon as the stock went ex-dividend, which was 9:30 a.m. Thursday morning.
Over the past year, Apple was under a lot of pressure from institutional investors to return some of its cash to shareholders, which it finally did last April in the form of a massive stock buyback and a relatively generous dividend.
Investors who are in Apple for the long term do enjoy the benefits of what is, at the stock's current price, a 2.6% annual return.
But so do the traders who are in it for a quick buck, and I suspect they are the ones who drove the stock down Thursday morning.
Apple recovered somewhat, closing Thursday at $461.01, down only $3.97 (0.85%) for the day.