Boosted by strong overall earnings, recent political harmony, and increasing momentum, the S&P 500 Index (^GSPC -0.88%) continued its remarkable eight-day run on Friday -- its longest winning streak since 2004 -- advancing more than 0.5% to close above 1,500 for the first time in more than five years. In the middle of such widespread optimism it's easy to forget that not all stocks are rising with the tide. These three S&P 500 companies help to drive that point home today. 

Mining equipment manufacturer Joy Global (JOY) was today's biggest loser, shedding some 4.1%. It wasn't an earnings miss that dinged the shares -- the company doesn't report until late February -- but rather a bleak outlook from its imposing rival Caterpillar. The sub-$7 billion Joy, with just a fraction of Caterpillar's $62 billion market cap, took a big hit after Caterpillar announced a decline in its own retail machinery sales today. Investors fear a slowdown in the global industry won't be very joyous for them at all. 

Our second laggard of the day was Weyerhaeuser (WY 0.38%). Shares in the lumber producer and homebuilder fell 1.8%, despite a quarter where profits more than doubled from the year before. Unconvinced by results that were driven by "non-strategic land sales," rather than core business performance, high raw materials costs (i.e., higher cost of lumber) highlighted one reason behind Friday's bleak close. 

The bad news for Ford (F 0.66%) investors is that its 1.4% stumble earns it the last spot among today's market underperformers. The good news? Friday's decline had nothing to do with weaknesses in Ford as a company. In fact, the sell-off was fueled by an analyst downgrade, one more motivated by the stock's recent run-up than the business' fundamentals. Citing its impressive products and management, a Barclays analyst became the second to downgrade the stock this week, asserting that he thinks the company is currently fully valued.