For the fifth consecutive day, the Dow Jones Industrial Average (^DJI -0.98%) continued its losing streak. Because investors and traders have yet to see any meaningful progress with only three days left until the U.S. falls off the fiscal cliff, the markets moved lower across the board today. Every last one of the Dow's 30 components closed in the red, and the index ended the day down 158 points or 1.21%. The Dow now sits at 12,938. Both the S&P 500 (^GSPC -0.46%) and the Nasdaq (^IXIC -0.64%) also had rough days as they slid lower by 1.1% and 0.86%, respectively.

This afternoon, I explained why the three biggest Dow losers at the time were Hewlett-Packard (HPQ 0.11%), ExxonMobil (XOM 0.23%), and Chevron (CVX 1.04%). The three companies were not just the top three losers at 1 p.m., but managed to end the day holding their spots. Read about what caused those stocks to fall by clicking here or stick around to learn why Microsoft (MSFT -2.45%), United Technologies (RTX 0.68%), and Boeing (BA 1.51%).

So why did they fall?
Shares of Microsoft ended today down 1.52%. While the likely culprits for the move lower were investors' concerns over the fiscal cliff and what will happen to the economy if we tumble off the edge, it was announced that the British education and media publisher Pearson agreed to purchase a 5% stake in Barnes & Noble's (BKS) Nook Media unit for $89.5 million. Back in April, Microsoft invested $300 million into the company, and it will still own 16.8% of the business after this new deal is finished. While it makes sense for Pearson and the Nook to team up to sell textbooks and other digital educational materials, I still don't see what benefit Microsoft gains by owning part of the Nook business. 

Two other big drags on the Dow today were United Technologies and Boeing, which fell by 1.54% and 1.5%, respectively. Both companies are interconnected with the Department of Defense and if we go over the cliff, the U.S. Defense budget will automatically be cut. That will in turn hurt and lower the two Dow components' revenue and profits.

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