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: On Wednesday, for no particular reason (none that anyone knows about, at least), shares of titanium dioxide producer Kronos Worldwide (NYSE: KRO) suddenly spiked 12%.

So what: What caused the spike? I'm not exactly sure. Shares of parent company Valhi (NYSE: VHI) were mostly unchanged in Wednesday trading, so that doesn't seem related. Allegheny Tech (NYSE: ATI) , a supplier of titanium airplane parts, re-upped a supply agreement with Boeing (NYSE: BA) -- but this, too, seems a red herring. Yes, Kronos and Allegheny both deal in titanium. But Kronos uses smaller amounts to produce pigments and other specialty chemicals -- not solid, functioning airplane parts.

Best guess? Investors are following the lead of Kronos CEO Steve Watson, who filed a disclosure with the SEC yesterday confirming his purchase of 5,000 shares of his company's stock.

Now what: Whatever the spark was that ignited a fire under Kronos' stock, I suspect that buying the shares is as good an idea today as it was when I pronounced Kronos a bargain back in August. According to Yahoo! Finance, Kronos shares cost only about nine times earnings today, while the stock is pegged for 20% annual growth over the next five years. To me, that sounds like a bargain.

Wondering if Rich is right about that? Add Kronos Worldwide to your Fool Watchlist and find out.