Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of NL Industries (NYSE: NL) surged as much as 14% before ending the session up 7%. The company appears to have been following the action in its parent, Valhi (NYSE: VHI), which closed up more than 18%.

So what: The company may also be benefiting from institutions following insiders. CEO Harold Simmons was a buyer back in February. A Grand Selloff may have enticed him back in, and a rush of institutional investors along with him.

Now what: I know, I'm speculating. But would anyone really be surprised? The stock trades for just six times earnings and two times book value, cheap multiples when compared with its industry peers. Is that enough? Would you buy shares of NL at these levels? Weigh in using the comments box below.

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