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

Following a mid-week spike that sent the S&P 500 Index (SNPINDEX:^GSPC) to all-time highs on Wednesday, the index sold off going into the weekend, losing 12 points, or 0.7%, Friday, ending at 1,709. Aside from the simple urge to take gains, worries over what will happen with the U.S. debt ceiling sent stocks spiraling lower. Similar concerns caused a downgrade to America's creditworthiness in 2011, a move that prompted a sharp stock market sell-off.

One of the worst performers in the S&P today was Newmont Mining (NYSE:NEM), logging a second straight day as one of the index's most severe laggards. Falling 5.7%, the gold and copper miner struggled as the price of gold slumped today. Gold spiked on Wednesday -- so did Newmont, which surged more than 8% that day -- as the Fed announced a continuation of its easy money policies to stimulate the economy.

Sprint (NYSE:S) followed the telecom sector's lead -- telecoms were the weakest area of the market Friday -- dropping 3.5%. Competition is heating up among the big wireless carriers in the U.S., as Verizon just completed the biggest bond offering in history last week. With Verizon raising cash to reacquire its U.S. wireless business, Sprint is being forced increasingly to compete on price, and pressure its margins in order to have a chance to gain market share. 

Lastly, Caterpillar (NYSE:CAT) shares lost 3.4%, as the machinery and equipment giant announced sales at its global dealerships slumped 10% in the last three months. The only market in which Caterpillar dealers actually increased sales was the North American market, where revenue rose by a meager 1%. The Asia-Pacific market was the area of the most severe order declines, slumping 30% in the period. If there's a silver lining to today's numbers, it's that the weak figures give the company easier comps to display growth going forward.

Fool contributor John Divine has no position in any stocks mentioned. You can follow him on Twitter @divinebizkid and on Motley Fool CAPS @TMFDivine.

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