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 Telephone & Data Systems (NYSE:TDS) have dropped today by as much as 15% after the company reported earnings.

So what: Total operating revenue came in at $1.37 billion, a modest increase of 3%. Earnings per share of $0.27 fell far short of the $0.43 per share that investors were expecting. CEO LeRoy T. Carlson, Jr. said profitability was hurt by increasing smartphone subsidies, declining regulatory support and investment spending.

Now what: The company's U.S. Cellular business unit also announced that it was selling spectrum and customers to Spring Nextel (NYSE: S). TDS also narrowed its guidance ranges and now expects U.S. Cellular service revenue in the range of $4.07 billion to $4.13 billion. Telecom operating revenue should be in the ballpark of $850 million to $860 million.

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Fool contributor Evan Niu, CFA, 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.