I've noticed on a few stocks (NYSE:WHR, NYSE:PHM), that during extended hours trading, the bid/ask spread becomes extremely large. For example:
Mar14th WHR closed at ask $78.10, and bid $78.30, and then after hours, quickly change to $77.72/$78.09, then 6pm it was $76.60/$78.09. When it hit midnight, $76.50/$80.25.
That's a really big spread in comparison to where it close at, and then where it opened at ($77.89/$78.56) the next morning.
Is this just a matter of, after hours there's fewer brokers buying and selling and it's a tougher market? Or is there something else at play to cause such a large spread?