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 Milwaukee-based grocer Roundy's (NYSE: RNDY) were spoiling today, falling as much as 25% in intraday trading after the company reported second-quarter results.

So what: You know what investors hate to see during earnings season? Their company missing earnings estimates. You know what they hate even more? A disappointing forecast for the quarters ahead. In its second-quarter earnings release, Roundy's did both.

For the second quarter, the operator of Pick 'n Save and Copps reported earnings per share down 28% from last year, to $0.42. Total net income was up from last year, but the company's share count increased drastically. Wall Street analysts were expecting $0.43 in EPS. Revenue climbed 1.7%, but the $997 million tally was short of the $1 billion that analysts had forecasted.

Now what: What was probably even more painful for investors today was that Roundy's also walked back its guidance for the year. The company now sees revenue growing just 1% to 2% for the year, as compared with its previous forecast of 2.5% to 3.5% growth. On the bottom line, management expects between $1.10 and $1.24 in per-share profit, down from the previous range of $1.30 to $1.42. The consensus from Wall Street had been $1.34 for the year.

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