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 railcar maker Greenbrier Companies (NYSE:GBX) rolled off a cliff today, falling as much as 19%, after its earnings report came up short.

So what: Earnings per share fell to $0.26, below the $0.42 it made a year ago, and well off of the $0.57 that analysts had expected. A delay in deliveries and a higher tax rate were partly responsible for the shortfall, as revenue of $443 million was also far off estimates at $498 million. The company also sharply cut back its 2013 forecast, saying it only expected to deliver 11,500 to 13,000 railcars, down from the 15,000  it delivered previously this year.

Now what: Orders in the quarter were down 45% to 2,900 railcars, indicating that more tough times could be ahead. Greenbrier is highly tied to energy markets, as most of its cars are used to carry frack sand and oil. That market does not appear to be going anywhere, and shares are already cheap; so, even based on this poor earnings report, I see no reason for investors to flee now. 

Jeremy Bowman has no positions in the stocks mentioned above. The Motley Fool has no positions in the stocks mentioned above. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.